Exploring the Mechanisms of Regional Environmental Collaborative Legislation in China: Policy Effectiveness, Practical Challenges, and Policy Suggestions

Abstract

The legislation for regional environmental collaboration is of significant importance in enhancing the effectiveness of environmental protection. The existing literature focuses on the power struggle between central and local governments regarding environmental regulation within the realm of regional environmental governance, lacking an examination of the collaborative governance mechanisms and their effectiveness. Therefore, this study takes China’s regional environmental collaborative legislation as its research object. It employs a difference-in-differences model to test the effectiveness of regional environmental collaborative legislation concerning environmental governance and conducts a qualitative analysis to examine the current practical challenges facing regional environmental collaborative legislation. The quantitative analysis results indicate that regional environmental collaborative legislation can effectively suppress the emission of environmental pollutants. Specifically, the implementation of regional environmental collaborative legislation results in a 19.7% reduction in prefecture-level wastewater emissions and a 26.6% reduction in sulfur dioxide emissions. Qualitative analysis results show that regional environmental collaborative legislation currently faces challenges such as localism, difficulties in legislative authority allocation, and a lack of cooperation mechanisms. Therefore, this paper proposes to establish a collaboration platform, balance the interests of stakeholders, and improve the allocation mechanism of environmental regulatory powers in order to better optimize the regional environmental collaborative legislation and enhance the government’s environmental governance capacity.

1. Introduction

China’s economy has transitioned from a phase of high-speed growth to a stage of high-quality development, a shift highlighted in the report of the 20th National Congress of the Communist Party of China. This report emphasizes the critical role of greening and low-carbon development in achieving high-quality growth, thereby delineating a future direction for both environmental governance and economic development. This necessitates a stronger emphasis on regional environmental governance to stimulate industrial restructuring, promote a positive economic cycle, and garner additional financial and technical support for environmental management efforts. In this context, the Chinese government and its associated departments have prioritized the construction of a social ecological civilization, encapsulating this commitment with the slogan, “Building an ecological civilization is essential for the people’s wellbeing and the nation’s future”. This has spurred explorations in governance models for regional and local environmental protection at both central and local government levels.

From a global perspective, regional environmental issues are common challenges faced by the international community. Globally, there are two collaborative governance models based on different political systems for regional environmental governance. One is the environmental federalism governance model, led by federal states, and the other is the regional environmental collaborative legislative model, led by unitary states [1]. The political system has a particularly significant impact on the collaborative governance model. For instance, the United States’ federal system brings about environmental federalism in environmental governance, with the power struggle between the federal government and state governments being at the core of environmental federalism [2]. The federal government and state governments in the United States have been in contention over the interpretative authority regarding “waters of the United States” under the Clean Water Act [3]. The competition between central and local governments can also lead local governments to strengthen the overall environmental governance capacity of the country through local initiatives. The multi-level governance (MLG) formed by the European Union and its member states in regards to global climate and energy governance is a typical example [4]. Germany, a federal state and a pioneer representative of the European Union, has seen more than 140 municipal governments formulate the goal of obtaining 100% of their electricity from renewable sources. This initiative has led to 30% of the country becoming powered entirely by renewable energy [5].

However, in the complex realm of regional environmental governance, particularly concerning air pollution and river management, the power struggle between central and local governments under environmental federalism, along with the limited effectiveness of individual local initiatives in addressing cross-regional environmental issues, has underscored the increasing importance of local and regional cooperation. In the realm of air pollution governance, although the US Congress enacted the 1970 Clean Air Amendments, requiring the attainment of uniform air quality standards, this goal was ultimately not achieved due to the differences in implementation by local governments in environmental governance decision making [6]. In river management, local governments in unitary states are more likely to form river partnerships based on the overall objectives of national environmental regulation. For instance, the Catchment Based Approach (CaBA), initiated in 2013 by the UK Government, employs a collaborative approach to water management throughout England. Over the six years since its inception, there have been 106 river catchment partnerships established [7]. Japan, another unitary state in East Asia, has also adopted inter-municipal cooperation (IMC) for regional waste management [8]. As the largest unitary state, the relationship between the central government and local governments in China is one of leadership and being led. Therefore, the power struggle between the central government and local governments is not the core issue in regional environmental governance. The governance model adopted by the Chinese government for regional environmental issues is regional environmental collaborative legislation. This governance model mainly focuses on cooperation and conflict among local governments, rather than on the power struggle between the central government and local governments.

This study focuses on China, the largest unitary state, to investigate its adoption of the regional environmental collaborative legislation in addressing regional environmental issues. This approach is not only based on global governance practices in response to regional environmental issues, but it also seeks to fill the research gap regarding the participation of unitary states in regional environmental governance. The research questions addressed in this study are as follows: Is the regional environmental collaborative legislation adopted by China effective in addressing regional environmental issues? What are the current practical challenges facing existing regional environmental collaborative legislation? How should the regional environmental collaborative legislative model be optimized in the future to enhance environmental governance capabilities? Therefore, this research aims to evaluate the effectiveness of the regional environmental collaborative legislation through qualitative research and to examine the practical challenges of this model through normative analysis, providing valuable institutional recommendations.

The regional environmental collaborative legislation aims to address the public, dynamic, and holistic nature of environmental challenges, with a specific focus on cross-regional governance [9]. This approach emphasizes breaking down administrative and interest-based barriers, fostering an integrated and synergistic approach to regional environmental law. This form of legislation addresses the issue of fragmentation in environmental regulations formulated by individual regions, thereby enhancing the overall effectiveness of environmental protection. It has gradually gained attention and application from both central and local governments. Guided by the principles of legislation for regional environmental collaboration, China’s environmental legislation philosophy is becoming more coherent, its legal frameworks are continually being refined, and governance institutions are being optimized, leading to significant improvements in environmental management [10]. However, regional environmental collaborative legislation may still face the following challenges: firstly, the gap caused by regional disparities in political status, economic development, geographical conditions, and cultural traditions; secondly, whether regional environmental collaborative legislation can mobilize the governance role of multi-level local legislative entities across regions; thirdly, conflicts and coordination issues between regional environmental collaborative legislation and local environmental legislation.

In the introductory context of regional environmental governance, the scholarly discourse reflects a significant interest in and response from both theoretical and practical domains.

Firstly, a substantial volume of literature has delved into the necessity of regional environmental collaborative legislation. Briffault (2000) posits that regionalism, as a theory opposed to localism, suggests that future societal governance should shift from localism to regionalism. He further notes that the application of regional policies can effectively address issues of regional environmental protection [11]. Meng (2016) specifically examines the Beijing—Tianjin—Hebei region, advocating for the enhancement of local environmental collaborative legislation and the establishment of a regional environmental legal framework. This approach is seen as vital for providing strong legal backing to jointly improve the regional ecological environment [12]. Wang (2018) extends this discussion by arguing that regional environmental legislation is a critical requirement for the integrated economic development of regions. Wang emphasizes the role of legal measures in balancing rights and interests and in upholding stability and development within regional economies [13]. Furthermore, Huang and Li (2023) contribute to this discourse by asserting that regional environmental legislation, steered through laws, not only guides regional environmental law enforcement cooperation but also lays the groundwork for judicial coordination within the region. They contend that such legislative initiatives enhance the environmental protection consciousness of governments, businesses, and the public, thereby augmenting the regional capability for environmental rule of law and consequentially, improving the regional environmental quality [14].

Secondly, several scholars have also elucidated regional environmental collaborative legislation from a practical perspective, focusing on its models, mechanisms, and systems. Yang and Qiu (2016) suggest that the top-level design of regional environmental collaborative legislation models should incorporate the concept of fiscal cooperation [15]. Wang and Wang (2016), beginning with the environmental governance issues in the Beijing—Tianjin—Hebei region, analyze the necessity of regional environmental collaborative legislation. They summarize the current status of multi-centric governance and environmental collaborative legislation theories and practices, proposing a model based on “four centers”, consisting of government, businesses, the public, and non-governmental environmental organizations [16]. Si and Zhang (2021) present three distinct types of legislation models based on dynamic mechanisms: the “hierarchical authority” model, exemplified by the Beijing—Tianjin—Hebei region, the “inter-governmental consultation” model, represented by the Yangtze River Delta, and the “campaign-style” model, illustrated by the Fen-Wei Plain area [17]. Chen (2023) views the regional environmental collaborative legislation system as a cyclic system integrating “causes, agents, dynamics, actions, and outcomes”. This study describes the legislation mechanism as an organic system comprising organizational, dynamic, operational, feedback, and interactive mechanisms [18].

Thirdly, emerging literature has begun to increasingly focus on the impact of regional environmental collaborative legislation on environmental governance, discussing its effects through both qualitative and quantitative analyses. In terms of qualitative analysis, Zhou (2020) explores the improvement directions of regional environmental collaborative legislation from aspects like models, dynamics, and pathways, emphasizing the significance of intergovernmental cooperation under China’s decentralized system for environmental governance [19]. Suo and Li (2021) analyze the structural attributes and evolutionary characteristics of regional environmental collaborative governance from a perspective of multi-entity co-governance, constructing an environmental governance framework under regional environmental collaborative legislation [20]. In the realm of quantitative analysis, Han (2017) employs the bootstrap-DEA model to assess the efficiency of China’s ecological environment collaborative governance [21]. The study discovers significant regional disparities in China’s environmental collaborative governance, which exhibit a U-shaped characteristic of initial convergence, followed by divergence. Zhang and Shang (2018) utilize a coupling assessment model to evaluate the green development collaborative performance in the Yangtze River Delta and the ecological environmental collaborative governance performance of 45 cities in Western China [22]. Their findings reveal a strong pollution reduction effect of regional environmental collaboration and explore differentiated pathways for the practical implementation of regional environmental collaborative legislation to promote pollution reduction.

Overall, the existing research has predominantly focused on explicating and analyzing the concepts and mechanisms of regional environmental collaborative legislation, often adopting a relatively singular perspective. However, the issue of regional environmental collaborative governance cannot be thoroughly understood through a singular lens; it demands a profound grasp of its fundamental problems. The reviewed studies lack a focused examination of the research question, centering primarily on the issues related to regional environmental collaborative legislation. As an important legislative type, regional environmental collaborative legislation exhibits distinct characteristics in regards to policy effects, practical dilemmas, and systemic optimization. Moreover, the existing literature tends to employ basic research methods to discuss the environmental governance effects of regional environmental collaborative legislation, lacking sufficient and effective empirical evidence, particularly from a quantitative analysis standpoint. Building upon the foundation of the existing literature, this paper explores the normative documents and governance outcomes of regional environmental governance. It employs a difference-in-differences model to empirically test the policy effects of regional environmental collaborative legislation, aiming to explore the causal relationship between norms and governance outcomes. Further, to avoid turning regional environmental governance into an “ivory tower” concept, this paper investigates the governance effectiveness and practical manifestations of regional environmental collaborative legislative mechanisms under the guidance of legislative texts. Based on this, it proposes pathways to enhance the regional environmental collaborative legislative mechanism. This has significant practical implications for promoting the high-quality integrated development of regional economies and societies.

To examine the effectiveness of regional environmental collaborative legislation in regards to environmental governance and to analyze its practical challenges, this paper first meticulously sorts out the legislative documents concerning regional environmental collaboration in three major Chinese regions: the Three Northeastern Provinces, the Yangtze River Delta region, and the Beijing—Tianjin—Hebei region. It provides a comprehensive analysis and discussion of the legislative models and distinctive features of regional environmental collaboration in these areas. Building on this, the study utilizes prefecture-level data from China spanning 2010 to 2019 to construct a difference-in-differences model (DID). This model empirically tests the policy impact of regional environmental collaborative legislation on prefecture’s environmental pollution. In conjunction with the current state of regional environmental collaborative legislation in these three regions, the paper delves into the practical challenges and optimization paths inherent in implementing this legislation. The findings of the study indicate that regional environmental collaborative legislation effectively reduces urban environmental pollution levels in the collaborative regions, significantly demonstrating its efficacy in environmental governance. However, the current practice of regional environmental collaborative legislation in these areas faces challenges, including severe local profit-seeking, a unidimensional legislative hierarchy, and insufficient collaborative mechanisms. Therefore, the paper suggests the need to establish cross-regional environmental protection cooperation mechanisms and negotiation platforms, while also improving the horizontal collaboration mechanisms and vertical delegation mechanisms for regional environmental legislation. Through both internal and external drivers, this optimization and transformation of regional environmental governance can be achieved, providing essential institutional support for regional environmental legislative cooperation.

2. Institutional Background: The Practical Characteristics of Regional Environmental Collaborative Legislation Mechanisms

The mechanism of regional environmental collaborative legislation, which emphasizes inter-local cooperation rather than the division of power between central and local governments, reflects the reality of the new regionalism theory in environmental governance strategies. The new regionalism theory suggests that neither localism, advocating for local autonomy, nor the regional general-purpose governments proposed by old regionalism theories, are the most effective ways to address regional environmental issues. Instead, voluntary collaboration across regions is seen as the future trend [23]. Therefore, before evaluating the impact of regional environmental collaborative legislation on environmental governance, it is essential to examine the diverse models of “voluntary collaboration” within regional environmental collaborative legislation.

The model of regional environmental collaborative legislation in China did not emerge solely as a result of explicit provisions in the legislative law. Drawing on the country’s traditional “pilot policy” approach, the Three Northeastern Provinces had already initiated the precedent for regional collaborative legislation in 2006 [24], with the Yangtze River Delta region following suit in 2007, developing a unique collaborative legislative model. Although the collaborative legislation in the Beijing—Tianjin—Hebei region, centered around Beijing, was developed later, it also presented a distinctive model of cooperation. Thus, it is imperative to first trace the historical trajectory of these three collaborative legislative models. After analyzing the specific frameworks of each model individually, an abstracted analysis focusing on the regional environmental collaborative legislative model itself should be conducted [12].

With the decision to amend the Legislation Law passed by the 14th National People’s Congress in 2023, regional collaborative legislation was officially recognized for its legal status and effectiveness. However, Article 83 of the Legislation Law merely states that “provinces, autonomous regions, municipalities directly under the Central Government, and cities with districts, autonomous prefectures may establish mechanisms for regional collaborative legislative work”, without detailing the practical models of such legislation. Therefore, it is necessary to analyze the existing practices of regional environmental collaborative legislation prior to this amendment. Based on the “pilot policy” initiatives already in place, this analysis aims to anticipate a collaborative model that aligns with the amendments to the Legislation Law [25].

2.1. Regional Collaborative Legislation in the Three Northeastern Provinces: A Semi-Intensive Legislative Model

The Three Northeast Provinces specifically refer to the three provinces in the northeastern part of China: Heilongjiang, Jilin, and Liaoning. (Refer to the yellow area in Figure 1 for details) According to the latest data, the population of the urban agglomeration in the Three Northeast Provinces has reached 98.51 million, and the GDP total reached CNY 5.96 trillion in 2023, making it the most densely populated region of resource-based cities in China. As China’s old industrial base, the Northeast region has made remarkable contributions to China’s socio-economic development by vigorously developing heavy chemical and resource-based industries based on the mineral resources in the region.

Drawing on China’s tradition of “pilot policies”, these provinces initiated a pioneering regional legislative collaboration framework as early as 2006, with the signing of the “Three Northeast Provinces Governmental Legislative Collaboration Framework Agreement”. This framework introduced a three-tiered model of legislative collaboration—intensive, semi-intensive, and dispersed—among which the Three Northeast Provinces adopted a semi-intensive model. This model entails one province taking the lead in drafting legislation on issues of mutual concern, with the other two providing support throughout the process. Given the absence of statutory provisions for regional collaborative legislation at the time, the framework explicitly designated provincial governments as the legislative bodies, confining the level of legislation to provincial government regulations and adopting a relatively uniform legislative model. The initial batch of nine legislative collaboration projects all followed the semi-intensive model, without any specific plans for environmental legislation.

Firstly, in terms of legislative subjects, as the concepts of ecological protection and environmental governance gain widespread acceptance, the Three Northeast Provinces have progressively developed specialized legislation aimed at protecting specific natural areas, such as the Songhua River Basin, black soil lands, and wetlands, prioritizing natural regions or elements for targeted protection. Examples include watershed environmental legislation (Heilongjiang Province, Jilin Province: “Songhua River Basin Water Pollution Prevention Regulations”), soil environmental legislation (Heilongjiang Province, Jilin Province: “Black Soil Land Protection Regulations”), and wetland environmental legislation (Heilongjiang Province, Jilin Province, Liaoning Province: “Wetland Protection Regulations”). These laws are characterized by identifying unique conservation targets within administrative regions, predominantly adopting the semi-intensive legislative model and providing guidance for administrative law.

Secondly, there is a lack of uniformity in the levels of legislation. Although the collaborative legislation in the Three Northeast Provinces is based on a governmental legislative collaboration framework agreement, the practice of establishing legal norms is not confined to local government regulations. Some manifest as local regulations enacted by the Local People’s Congresses, acting as the legislative bodies, while others are normative documents of a lower efficacy level, or administrative agreements without external legal force.

Thirdly, the phenomenon of non-collaborative local environmental legislation exists within environmental legislative collaboration. For instance, the “Songhua River Basin Water Pollution Prevention Regulations”, implemented by Heilongjiang and Jilin provinces, despite their similar timing and content, were enacted independently, with Jilin’s legislation preceding that of Heilongjiang. The legislation enacted by Heilongjiang Province aimed, in part, to align with Jilin Province’s legislation. While seemingly collaborative in form, both essentially constitute “local environmental legislation”.

Lastly, the aim of collaborative legislation is to guide collaborative enforcement to spur economic growth. This is manifested in the cooperation and division of responsibilities among administrative agencies, refining the content of administrative law enforcement [26], without substantively legislating the collaborative aspect. The initial purpose of establishing a framework for regional collaborative legislation among the Three Northeast Provinces was to facilitate legislative alignment and enforcement uniformity across the provinces, thereby revitalizing the industrial base of the Northeast and achieving significant economic development. Economic growth remained a common goal of regional collaborative legislation for a considerable period thereafter.

2.2. Regional Collaborative Legislation in the Yangtze River Delta: An Intensive Legislative Model

The Yangtze River Delta region is located in the downstream area of the Yangtze River in China, mainly including the provinces of Zhejiang, Jiangsu, and Anhui, as well as the municipality of Shanghai (refer to the orange area in Figure 1 for details). According to the latest data, the population of the urban agglomeration in the Yangtze River Delta has reached 235 million, and the GDP total reached CNY 30.50 trillion in 2023, making it one of the most active, open, and innovative regions regarding China’s economic development. The Yangtze River Delta region serves as an important platform for China’s participation in international competition, a vital engine for economic and social development, and a leader in the Yangtze River Economic Belt.

Its regional collaborative legislation includes the “Minutes of the Suzhou-Zhejiang-Shanghai Legal Cooperation Symposium”. Similar to the Three Northeast Provinces, the primary goal of legislative collaboration in the Yangtze River Delta was also to promote economic growth, encouraging economic collaboration, oppose local protectionism, and unify law enforcement efforts. Unlike the Three Northeast Provinces, where collaborative legislation began with the signing of administrative agreements, the aforementioned minutes only provided guiding principles and legislative concepts for collaboration, without establishing a specific legislative model or working mechanism. Moreover, since the minutes were jointly signed by the Legal Affairs Committees of the People’s Congresses, Government Legal Affairs Offices, and Law Societies of Jiangsu, Zhejiang, and Shanghai, their nature was not consistent with that of practical administrative agreements.

Scholars have categorized the collaborative legislative models in the Yangtze River Delta into “intensive, semi-intensive, and dispersed” types. Based on its collaborative characteristics, the region’s collaborative legislative model is primarily considered intensive. In practice, the Yangtze River Delta has developed various supporting mechanisms, such as legislative planning and collaboration mechanisms, information sharing mechanisms, and media cooperation mechanisms, gradually aligning closer to an intensive legislative model.

Since the 18th National Congress of the Chinese Communist Party, the Central Committee and the State Council have placed great emphasis on the construction of a social ecological civilization. The Yangtze River Delta has achieved fruitful outcomes in ecological and environmental legislative collaboration, mainly represented by two types, which are discussed below.

The first type is regional environmental collaborative legislation based on administrative regions, exemplified by the “Regulations on the Prevention and Control of Air Pollution”. The “Shanghai Municipal Regulations on the Prevention and Control of Air Pollution” includes a chapter on “Collaboration on Air Pollution Prevention and Control in the Yangtze River Delta”. Subsequent amendments or enactments of the “Zhejiang Provincial Regulations on the Prevention and Control of Air Pollution” and the “Jiangsu Provincial Regulations on the Prevention and Control of Air Pollution” all specify “Regional Joint Prevention and Control of Air Pollution”, with consistent content across the three jurisdictions, detailing information sharing, joint research, policy unification, and joint enforcement among other provinces and municipalities. While specifying collaborative legislation in a dedicated chapter, these regulations largely preserve the autonomy of each province or municipality in other provisions.

The second type is based on natural regions, which are also an integral part of local regulations. This category is further divided into two modes: “Decisions on Promoting and Ensuring the Construction of the Demonstration Zone for Ecological and Green Integrated Development in the Yangtze River Delta” and “Decisions on Promoting and Ensuring the Work on Fishing Bans in the Yangtze River Basin” by various provinces and municipalities. The former represents narrow regional environmental collaborative legislation, where the Standing Committees of the People’s Congresses in Jiangsu, Zhejiang, and Shanghai, after closely consulting and exchanging views, simultaneously issued regulations with identical content, providing comprehensive and directive guidance. The latter, led by Shanghai, and after soliciting written opinions from Jiangsu and Zhejiang, further unifies specific issues, with slightly different content in local regulations, representing broad regional environmental collaborative legislation.

2.3. Regional Collaborative Legislation in the Beijing—Tianjin—Hebei Area: A Dispersed Legislative Model

The Beijing—Tianjin—Hebei region, located in northern China, primarily includes Beijing, Tianjin, and Hebei (refer to the red area in Figure 1 for details). According to the latest data, the population of the Beijing—Tianjin—Hebei urban agglomeration has reached 114 million, with a GDP total of CNY 10.4 trillion in 2023, making it the most economically developed region in northern China. The Beijing—Tianjin—Hebei region serves as a vital economic hub and a world-class metropolitan area, playing a crucial role in China’s overall spatial development and regional coordinated development framework.

The inception of collaborative legislation in the Beijing—Tianjin—Hebei region can be traced back to the issuance of the “Opinions on Strengthening the Collaborative Legislation of People’s Congresses in the Beijing—Tianjin—Hebei region” in 2015. In accordance with the typology system previously discussed, which categorizes collaborative legislative models based on the degree of collaboration, the environmental collaborative legislation in the Beijing—Tianjin—Hebei region falls under the category of a “dispersed model”. This model differs significantly from the collaborative legislation models observed in the Yangtze River Delta and the Three Northeast Provinces. In the Yangtze River Delta and the Three Northeast Provinces regions, the legislative model is characterized by being “collaborative and consistent,” whereas in the Beijing—Tianjin—Hebei region, a “dispersed legislative model” prevails, resulting in a “collaborative but inconsistent” situation. This leads to what is often referred to as the “layered model” in the Beijing—Tianjin—Hebei region, with distinct legislative initiatives in Beijing, Tianjin, and Hebei.

Firstly, in terms of priority areas, the Beijing—Tianjin—Hebei region prioritizes infrastructure development and environmental protection, distinct from the Yangtze River Delta and Three Northeast Provinces, which prioritize economic growth and rapid development.

Secondly, regarding safeguard mechanisms, the Beijing—Tianjin—Hebei region’s local collaborative legislation has established safeguard mechanisms with organizational significance. This uniqueness can be attributed to the divergent development focuses and layered positioning among Beijing, Tianjin, and Hebei. Scholars have found through empirical testing that there are significant developmental disparities in the Beijing—Tianjin—Hebei region, and the three sub-regions have not yet entered a stage of coordinated development [27]. As outlined in the “Outline of the Beijing—Tianjin—Hebei Collaborative Development Plan”, Beijing serves as the political and cultural center of China, making it the core region for collaborative legislation. Tianjin leads in emerging industries, serving as a key area for legislative focus. Meanwhile, Hebei operates as an experimental zone for industrial upgrading, ensuring legislative support [28].

While the Beijing—Tianjin—Hebei region adopts a dispersed legislative model, the practical results of legislation are quite the opposite. Despite significant differences in the specific content of environmental collaborative legislation due to the diverse focuses and layered relations, the collaborative legislation achieves synergy in legal enforcement practices after enactment, effectively fulfilling its legislative objectives and intended outcomes [29]. This form of incongruence in structure but congruence in essence characterizes the collaborative model in the Beijing—Tianjin—Hebei region. The differentiation in collaborative legislation is most evident in the variations among the Beijing—Tianjin—Hebei region’s “Regulations on the Prevention and Control of Atmospheric Pollution”. Specifically, the legislation in Beijing is the most stringent, allowing for the formulation of local standards which are stricter than the national standards. Tianjin adopts a moderately strict approach, permitting the establishment of more stringent local standards, if no national standards exist. Hebei follows a relatively lenient path, requiring a deadline compliance when national standards are not met and aligning its standards closely with those of Tianjin. Additionally, the identification of polluting activities subject to penalties varies among the three regions. For instance, both Beijing and Tianjin prohibit outdoor burning of materials, such as asphalt, that pollute the atmosphere. Meanwhile, Hebei prohibits such activities in densely populated areas and other areas requiring special protection. Furthermore, the determination of penalty amounts displays discrepancies. Although all three regions set similar lower and upper limits for penalties related to unlawful activities, Beijing and Tianjin exercise more discretion in evaluating the severity of violations, while Hebei relies on the seriousness of the offense to determine penalty amounts.

The legislative phenomena mentioned above indicate that environmental legislation on atmospheric pollution in Beijing and Tianjin will be more stringently implemented here than in Hebei. This legislative diversity stands in contrast to the efforts in the Yangtze River Delta and the Three Northeast Provinces, where a consistent legislative model is pursued. This “dispersed legislative model” facilitates the gradual relocation of heavily polluting enterprises from Beijing and Tianjin to Hebei due to the more lenient local legislation. Subsequently, these enterprises leverage Hebei’s legislative framework to achieve industrial upgrading, contributing to the phased ecological protection of the Beijing—Tianjin—Hebei region.

3. Empirical Examination of the Policy Effects of Regional Environmental Collaborative Legislation

3.1. Data and Methodology

3.1.1. Data and Sample

The database used in this paper comes from the China City Statistical Yearbook, published by the National Bureau of Statistics of China, which comprehensively reports the socioeconomic development and urban construction of each prefecture-level city in China. We collected the prefecture-level pollution emissions, as well as the prefecture-level control variables, from the China City Statistical Yearbook. In addition, the relevant documents for regional environmental collaborative legislation come from the official website of the Chinese People’s Congress deputies and local government portals. We obtained the corresponding legislative documents through manual collection. Based on the above datasets, we finally construct balanced panel of data composed of environmental pollution emissions and legislative documents from a total of 299 prefecture-level cities from 2010 to 2019 for analysis.

3.1.2. Identification Strategy

To examine the casual relationship between regional environmental collaborative legislation and prefecture -level pollution emissions, we estimate the following specification, using the difference-in-differences model:

$$Pollutio{n}_{ict}=\alpha +\beta Trea{t}_c\times Pos{t}_t+{X^{\prime }}_{it}\gamma +{\lambda }_i+{\lambda }_t+{\epsilon }_{ict}$$

(1)

where Pollution_ict denotes environmental pollution emissions for prefecture i in province c at year t. Treat_c is a dummy variable that indicates the prefecture i in province c, which carries out regional environmental collaborative legislation. Post_t is a dummy variable, before and after the establishment of regional environmental collaborative legislation, taking the value of one after the legislation and onwards and zero otherwise. X_it is a vector of time-varying prefecture-level control variables. In addition, we introduce prefecture-specific and year-specific fixed effects in the model equation to capture factors that alter at the prefecture- and year-level. ε_ict is an idiosyncratic error term, controlling for other unspecified factors. We focus on the coefficient β of DID term Treat × Post, which examines the causal effect of regional environmental collaborative legislation on prefecture-level pollution emissions.

3.1.3. Variable Measurement

Measurement of regional environmental collaborative legislation. A key issue in this paper is the measurement of regional environmental collaborative legislation. We manually collected regional environmental collaborative legislation documents from 2010 to 2019 in the Three Northeast Provinces, the Yangtze River Delta Region, and the Beijing—Tianjin—Hebei region from official website. Specifically, if a prefecture-level city in the above three regions proposes relevant legislative documents for regional environmental collaborative legislation, we regard it as a city carrying out regional environmental collaborative legislation, which provides important support for our subsequent identification of treatment groups and control groups. Through manual collection and identification, we determine that the research sample used in this paper includes a total of 64 prefecture-level cities that carry out regional environmental collaborative legislation (we call this the treatment group) and 235 prefecture-level cities that do not carry out collaborative legislation (i.e., the control group).

Measurement of pollution emissions. Using data from the China City Statistical Yearbook, we employ several pollutants to gauge prefecture-level pollution emissions. The China City Statistical Yearbook reports several types of pollution indicators at the prefecture level, such as wastewater emissions, flue gas, soot, and sulfur dioxide emissions (SO₂). Hence, we adopt wastewater emissions and sulfur dioxide emissions, which are reported in the most detail, as our dependent variables in this paper.

Control variables. We collect a set of prefecture-level variables to be used as controls in our empirical model to mitigate the problem of omitted variables. The control variables are constructed as follows: (1) LnPgdp is the natural logarithm of the prefecture-level GDP per capita; (2) LnPop is the natural logarithm of the prefecture-level total population; (3) Density is the population density, measured by the proportion of population to total land area; (4) Indstr is defined as the industry structure, measured by the proportion of added value of the second industry to the GDP; (5) Fiscal is the natural logarithm of the prefecture-level government fiscal expenditure. The summary statistics of the main variables used in this paper are presented in

Table 1. Summary statistics.

Variable	Obs	Mean	Std. Dev	Min	Max
LnWater	2990	8.061	1.389	0.693	11.477
LnSO2	2990	9.995	1.335	0.693	13.258
Treat × Post	2990	0.026	0.159	0	1
LnPgdp	2990	10.641	0.593	8.576	13.056
LnPop	2990	5.820	0.785	2.160	8.137
Density	2990	5.726	0.925	1.609	7.882
Indstr	2990	0.469	0.109	0.106	0.897
Fiscal	2990	0.214	0.154	0.044	2.349

.

3.2. Empirical Results

3.2.1. Baseline Results

In this section, we provide our baseline results on the causal effects of regional environmental collaborative legislation and pollution emissions. We add control variables in a stepwise manner to estimate Equation (1) as our baseline regression. We further consider the robust standard errors of clustered prefectures to address the serial correlation and the effects of the heteroskedasticity problem on the estimation results.

Table 2. Baseline results.

	Dependent Variable: Pollution Emissions
	(1)	(2)	(3)	(4)
	Wastewater Emissions		Sulfur Dioxide Emissions
Treat × Post	−0.183 ***	−0.197 ***	−0.284 ***	−0.266 ***
	(0.058)	(0.058)	(0.065)	(0.067)
LnPgdp		−0.191 ***		−0.091
		(0.071)		(0.072)
LnPop		0.887 ***		−0.257
		(0.164)		(0.165)
Density		−0.280		−0.322
		(0.282)		(0.298)
Indstr		0.935 ***		1.163 ***
		(0.347)		(0.304)
Fiscal		−0.178		0.250
		(0.130)		(0.196)
Prefecture FE	Yes	Yes	Yes	Yes
Year FE	Yes	Yes	Yes	Yes
N	2990	2990	2990	2990
Adj. R	0.921	0.923	0.880	0.881

Note: *** indicates significance at 1%. Standard errors in parentheses are robust and clustered.

reports the baseline results. Columns 1 and 3 report a simple DID specification that only includes the DID estimator and fixed effects. Our DID estimator, Treat × Post, is statistically significant and negative, suggesting that prefecture-level wastewater emissions and sulfur dioxide emissions significantly decreased after the establishment of regional environmental collaborative legislation. In columns 2 and 4, some time-varying prefecture-specific characteristics, such as GDP per capita, total population, population density, industrial structure, and fiscal expenditure, are contained in the regression. We find that the DID estimator is still significantly negative, while the estimated coefficients of the controls are consistent with our expectations. As for the control variables, the coefficient of the GDP per capita is significantly negative at the 1% significance level, indicating that prefectures with higher levels of economic development are able to suppress their wastewater emissions, to a greater extent. In addition, the estimated coefficients of population size and industrial structure are significantly positive, which means that prefectures with a high population size and a high industrialization proportion will significantly increase their prefecture-level wastewater emissions. The significant impact of industrialization on pollution emissions also holds true in the examination of sulfur dioxide emissions. However, the estimation results indicate that population density and fiscal expenditure do not have a significant impact on prefecture-level pollution emissions. Overall, the baseline results in Table 2 demonstrate that regional environmental collaborative legislation significantly enhances the environmental governance capabilities, thereby inhibiting pollution emissions at the prefecture level.

3.2.2. Validity Test

Parallel trend test. The key identifying assumption in our empirical strategy is that trends related to pollution emissions are the same among treated and untreated prefectures in the absence of regional environmental collaborative legislation. We therefore conduct a parallel trend test to check the identifying assumption of the difference-in-difference estimation. If the parallel-trend assumption holds, we should see no significant difference between the trend of treated and untreated prefectures in regards to pollution emissions before the policy shock. Specifically, we extend the DID specification to an event study by including a series of dummy variables in the standard regression to trace out the year-by-year effects of regional environmental collaborative legislation on pollution emissions. Using the following specification, we consider a ten-year window spanning from five years prior to legislation until five years afterwards.

$$Pollutio{n}_{ict}=\alpha +{\beta }_{1}Trea{t}_c\times Pos{t}_t^{-4}+\dots +{\beta }_{11}Trea{t}_c\times Pos{t}_t^{+5}+{X^{\prime }}_{it}\gamma +{\lambda }_i+{\lambda }_t+{\epsilon }_{ict}$$

(2)

where Post is a series of the pre- and post- policy year dummy variables. The vectors X are time-varying prefecture-level control variables. We should not expect any significant effects in the interactions; otherwise, that could indicate the existence of some underlying confounding factors. As shown in Figure 2, the solid line represents the estimated coefficient, and the dashed line represents the 95% confidence interval. None of the coefficients under the pre-treatment period reveal any statistical implications, and they show a similarly small economic magnitude. This indicates that the treated and untreated prefectures followed similar time trends at least five years before the policy shock. Then, note that pollution emissions decline rapidly two years after legislation, such that Post⁺³ is negative and significant at the 5% level, indicating that legislation effects have a two-year lag. In addition, with the adoption of the regional environmental collaborative legislation, the differences in pollution emissions between the treatment group and control group start to diverge. Overall, this common-trend test helps to resolve a concern regarding the anticipation effect and further confirms the validity of our identification strategy.

Placebo test. To address the concern concerning the non-random selection of the treatment group and the post time, we conduct a placebo test by randomly generating the treatment group and post time. Specifically, we first randomly select 10 provinces from the 31 provinces in the sample and assign them as a new treatment group; then, we randomly select a year from 2011 to 2018 (to make sure we have at least one year before the treatment and one year after the treatment for our DID analysis) as the year for legislation; finally, we construct a false regressor of interest, Treat_cfalse × Post_tfalse, from these two randomizations. Given the random generating process of the data, we expect that the results should show no significant effect; otherwise, it may indicate the misspecification of our difference-in-differences model. We therefore conduct this random test 500 times to enhance the veracity of the placebo test. The result is reported in Figure 3, the line represents the kernel density curve of the estimated coefficients, and the circles represent the p-value corresponding to each estimated coefficient. It is easy to observe that the distribution of estimates is centered around zero, showing an approximately normal distribution. The vast majority of estimates are not statistically significant (i.e., p-values > 0.05). Evidently, the result is highly insignificant, leading additional support to the validity of our research design.

4. Practical Challenges and Policy Suggestions Regarding Regional Environmental Collaborative Legislation

In the third section, we employed a difference-in-differences model to examine the impact of regional environmental collaborative legislation on the effectiveness of prefecture-level environmental pollution. We found that regional environmental collaborative legislation has a significant effect on reducing urban environmental pollution within collaborative regions. However, in practical terms, hindered by local profit-seeking behavior, a singular legislative hierarchy, and a lack of regional cooperation mechanisms, the full potential of regional environmental collaborative legislation cannot be realized. Therefore, in the face of these real obstacles, to fully harness the inhibitory effect of regional environmental collaborative legislation on urban environmental pollution, efforts should be directed towards establishing cross-regional environmental protection cooperation mechanisms and negotiation platforms for infrastructure development, strengthening horizontal collaboration mechanisms between regions, and improving vertical power distribution mechanisms among regions.

4.1. Practical Challenges: Practical Challenges in Regional Environmental Collaborative Legislation

4.1.1. Serious Local Profit-Driven Behavior in Regional Environmental Legislation

When examining the administrative regional divisions in China, it becomes evident that the profit-seeking behavior of local governments can impact the effectiveness of regional environmental legislation. The multifaceted roles of regional environmental legislation lead to local profit-seeking behavior and consequently, suboptimal legislative outcomes. The exercise of legislative authority in regional environmental collaborative legislation is achieved through negotiations among various regional administrative entities to address matters related to ecological environmental benefits, safety, natural resource development and management, ecological protection planning, and other related issues within the environmental region. This necessitates negotiation and the resolution of interrelated issues among different regions. However, when there are numerous stakeholders involved, it inevitably increases the complexity of negotiations. Balancing interests is a critical perspective when studying the establishment and implementation of agreements in regional environmental collaborative legislation. Local administrative entities tend to prioritize their self-interest, and in practice, their participation in collaborative legislation is often driven by the pursuit of maximizing their own interests, resulting in a situation where “localism” and “formalism” prevails. Localism not only generates issues of negative externalities, but neither is pure local autonomy conducive to solving regional problems [23]. This is particularly challenging for regions with relatively less developed and unbalanced regional economic growth, such as thein the case of Beijing and Hebei Province. If regional environmental legislation does not have the common pursuit of overall benefits as its goal, and if legislative entities do not participate in collaborative legislation as members of a shared interest community, it becomes difficult to harness the initiative and enthusiasm of local legislative entities. In such cases, the distinctive “collaborative” characteristic of collaborative legislation becomes superficial.

Strong local governments tend to utilize their authority to formulate environmental regulations that align with their specific regional characteristics, often prioritizing local characteristics over collaborative aspects. Regional collaborative development is an important strategic initiative in China, aimed at addressing common needs and challenges encountered during regional reform and development. However, administrative entities within their respective administrative boundaries often maintain relatively high administrative barriers between entities from other administrative regions. “Governance by law is the most stable and reliable mode of governance, and a complete legal system solidifies the foundation of the national governance system” [30]. Regional environmental collaborative legislation represents an innovative approach to local legislation and to some extent, helps break down administrative barriers, infusing fresh perspectives into environmental governance. However, the current practice of collaborative legislation in various regions of China typically involves separate deliberations for individual regions. Many legislative projects tend to favor local interests rather than to fulfill the needs of regional collaborative development. In other words, it exhibits legislative characteristics of “negotiation but separate legislation,” causing legislation to ultimately lean towards local characteristics rather than towards consolidating regional consensus. Regional environmental collaborative legislation should aim to align the practical requirements with the actual governance effects brought about by collaborative legislation, rather than to use the quantity of collaborative regional legislation as the sole criterion of the quality of it. Local entities should exercise legislative authority based on the actual needs of regional collaborative development and collaboratively enact regulations and rules with regional characteristics. However, based on the existing locally enacted regulations, this regional characteristic is not particularly prominent.

4.1.2. Singular Legislative Hierarchy in Regional Environmental Collaborative Legislation

From the perspective of the vertical legislative hierarchy in regions, the legislative level of regional environmental collaborative legislation tends to be relatively singular, and it does not fully mobilize the governance roles of multi-level legislative entities between regions. The distinctions among the majority of regional environmental collaborative legislative models mentioned in previous sections are mainly based on the consistency of local regulations among collaborative parties. However, there has been no differentiation in terms of legislative entities, effectiveness hierarchy, or legislative objectives [31].

Taking the effectiveness hierarchy as an example, the majority of scholars, legislative researchers, and legislative practices have limited their research scope on regional environmental collaborative legislation to local regulations enacted by provincial-level people’s congresses and their standing committees. This approach overlooks the fact that prefecture-level cities and autonomous prefectures can also establish mechanisms for regional collaborative legislation. As a result, within a province, there is often no vertical collaboration, and between two provinces, there is no collaborative legislative model at a lower level. For instance, in June 2023, the cities of Hegang and Jiamusi in Heilongjiang Province jointly implemented collaborative legislation for the protection of the Dulu River Wetland Nature Reserve, planning to enact the “Dulu River Wetland Protection Regulations”. However, upon investigation, it was found that this regulation is not in harmony with or connected to the provincial-level collaborative legislation for wetland protection among the Three Northeast Provinces.

Regarding collaborative legislative models for river basins, the majority of provinces tend to enact legislation independently within their respective jurisdictions. Only a few provinces have begun to explore collaborative legislative models for river basins [32]. Particularly for rivers that span two provinces and two prefecture-level cities, in the absence of a provincial-level collaborative legislative framework, there is often a situation where only two different provinces’ prefecture-level cities engage in collaborative legislation. The question arises of whether it is necessary to first establish a provincial-level collaborative legislative framework or whether the two prefecture-level cities can engage in collaborative legislation directly or through delegation. If it is deemed necessary to establish a provincial-level collaborative legislative framework first, it may constrain collaborative legislation, to some extent, at the prefecture-level city level. Conversely, it may lead to a disjointed situation where prefecture-level city-level collaborative legislation is not aligned with provincial-level collaborative legislation.

4.1.3. Inadequacy Regarding Regional Environmental Legislation Cooperation Mechanisms

From an overall perspective, there are insufficient regional collaborative mechanisms regarding environmental legislation, and local environmental legislation predominates over regional collaborative legislation. First, it is necessary to distinguish between regional environmental legislation and local environmental legislation. Some scholars argue that, while both narrow-sense regional environmental legislation and local environmental legislation primarily focus on ecological environmental protection, narrow-sense regional environmental legislation is based on the integrated development of multiple administrative regions, whereas local environmental legislation is based on a single administrative region. In other words, narrow-sense regional environmental legislation is a collaborative effort among multiple administrative regions to formulate legislation, while local environmental legislation applies only within a single administrative region [13]. Furthermore, narrow-sense regional environmental legislation needs to encompass the vast majority of ecological environmental protection requirements within that region, which is comprehensive, overarching, and possesses certain economic attributes.

In the comparative research conducted by the authors regarding the Three Northeast Provinces, the Yangtze River Delta, and the Beijing—Tianjin—Hebei regions, there is an ample supply of local environmental legislation, but there is a deficiency in narrow-sense regional environmental legislation. In the Yangtze River Delta’s regional environmental collaborative legislation, the “Decision on Promoting and Ensuring the Construction of the Demonstration Zone for Integrated Development of Ecological and Green Integration in the Yangtze River Delta” aligns with narrow-sense regional environmental legislation. However, the Three Northeast Provinces lack such related legislation. The existing widespread local regulations mostly fall under watershed legislation or local environmental legislation. Although they all fall under the broad-sense regional environmental legislation, there is a lack of narrow-sense regional environmental legislation to comprehensively coordinate regional environmental collaborative legislation. Empirical research indicates that in the absence of cooperation, fragmented governance models lead to the degradation of water bodies in transboundary river basins [33]. The relationship between narrow-sense regional environmental legislation and specific object-based local environmental legislation, such as watershed environmental legislation, pertains to the relationship between the general and specific provisions of environmental legal norms within this region. The absence of narrow-sense regional environmental legislation is akin to losing the general provisions, and the environmental legislation for specific objects can only rely on laws or administrative regulations as the superior legal basis, thereby losing the targeted and collaborative advantages of regional environmental legislation.

4.2. Policy Suggestions: Adaptive Measures for Regional Environmental Collaborative Legislation

4.2.1. Infrastructure Development: Establishing Cross-Regional Environmental Protection Cooperation Mechanisms and Negotiation Platforms

Establishing cross-regional environmental protection cooperation mechanisms and negotiation platforms is essential to provide institutional support for regional environmental legislative cooperation. A lack of cooperation mechanisms and communication channels is a significant challenge in the process of regional environmental legislative cooperation. Difficulties in reaching agreements and resolving differences often stem from conflicts of local interests [34]. New regionalism advocates for the voluntary cooperation of regional authorities, effectively addressing cross-regional challenges that localism fails to resolve. It also promotes regional equity among localities and fosters collaboration at the local level [35]. Therefore, cooperation and communication among governments and various stakeholders are crucial in cross-regional environmental protection. However, existing cooperation mechanisms are relatively weak, and communication channels are often not well-established, resulting in insufficient information sharing and increased conflicts of interest. In such a situation, regional environmental legislative cooperation faces challenges concerning making progress.

The implementation of environmental law should not be rigid. Negotiable implementation can enhance the flexibility of enforcing environmental laws [36]. The establishment of cross-regional environmental protection cooperation agencies and mechanisms, along with negotiation platforms, should consider the needs of all relevant parties. These platforms should facilitate information sharing and coordination, allowing regional governments to deeply collaborate and advance regional environmental legislative cooperation together. There are various forms of collaboration for stakeholder participation in environmental legislation, such as forming partnerships, holding ad hoc roundtable discussions, establishing regular advisory committees, and developing directive management plans or frameworks [37]. Balancing choices among multiple stakeholders is also a practical challenge in regional environmental legislative cooperation. Regional environmental legislative cooperation involves numerous stakeholders, including governments, enterprises, and residents, whose interests may conflict and differ. At this point, it is essential to balance economic, social, and environmental interests; to ensure public participation and adherence to the rule of law; to follow the principles of sustainable development; and to harmonize the interests of all parties involved.

4.2.2. External Drivers: Strengthening Horizontal Collaboration Mechanisms in Regional Environmental Legislation

Breaking away from a singular legislative hierarchy involves establishing and strengthening horizontal collaboration mechanisms between regions. The entities responsible for regional environmental collaborative legislation have been explicitly defined, with various legislative bodies playing a primary role in the collaboration mechanisms for regional environmental legislation. Although local governments are not the main legislative entities, they and their departments are significant participants in regional collaborative legislation. Addressing issues of regional environmental collaborative legislation also requires the joint efforts of governments at all levels, as well as relevant stakeholders.

On one hand, all legislative bodies should prioritize the overall interests of the region, breaking away from the notion of acting independently at the local level, and adopting a collaborative concept as a common principle. Relevant legislative working groups or special committees could be established, responsible for coordinating the legislative work of various departments and regions, while at the same time, strengthening the top-level design of regional environmental collaborative legislation, enhancing the guidance of the National People’s Congress and its special committees on regional collaborative legislation. Clear legislative principles should be established, including unified standards, cooperative governance, and the division of labor, to regulate the actions of legislative entities to avoid inconsistencies in the implementation of regulations and rules; legislation should adhere to the principle of differential management, taking into account the differences in environmental protection among regions, such as geographical location, resource conditions, development levels, etc., and adjusting measures and policies flexibly to adapt to the actual conditions of different regions. This approach would enhance the specificity and operability of legislation, allowing regions to adopt measures tailored to their specific conditions for better environmental protection outcomes.

On the other hand, “the competitive behavior among local governments in China is primarily determined by the system of fiscal decentralization and political centralization [38]”; thus, clarifying the functional positioning of local governments in regional environmental collaborative legislation can improve the specificity and operability of legislative work, promoting overall collaboration and governance of regional environments. Local governments have an important functional position in regional environmental collaborative legislation. Firstly, local governments should fulfill precise execution responsibilities, formulating specific environmental protection regulations within the legal framework set by the central government. Given the differences in environmental characteristics, resource distribution, and development needs between regions, local governments require flexibility and adaptability to legislate according to the actual conditions of their region. Secondly, local governments undertake important tasks in regards to resource allocation and supervision in regional environmental collaborative legislation. Local governments should allocate environmental protection resources according to the resource conditions of their region, ensuring that environmental protection efforts are effectively supported and guaranteed. Thirdly, local governments also need to supervise and evaluate the implementation of environmental protection efforts, identifying problems in a timely manner and taking appropriate measures to address them.

4.2.3. Internal Collaboration: Enhancing Vertical Decentralization Mechanisms in Regional Environmental Legislation

The regional environmental collaborative legislation collaboration mechanism includes both vertical collaboration from superior to subordinate legislation and collaboration among various levels of collaborative legislative entities. Currently, the regulations for China’s collaborative legislative collaboration mechanisms are relatively rudimentary, with unclear division of legislative authority among entities. Particularly, there is a lack of substantive collaborative legislation vertically across regions, and enthusiasm for such collaboration is not high. Therefore, it is necessary to establish an integrated environmental protection legal framework to improve the legal system and legislative procedures.

From the perspective of the level at which legislative power is exercised, the relationship between the provincial and municipal district levels regarding collaborative legislative powers should be clarified [39]. Legislative powers can be granted to municipal and district governments through authorization norms. For instance, it should be specified that “in the absence of provincial-level local environmental collaborative legislation, municipal-level local environmental collaborative legislation relevant to the city can be formulated; where provincial-level local environmental collaborative legislation exists, it should be further detailed according to the provisions of the provincial collaborative legislation and reported to the relevant ecological and environmental authorities for the record”.

While decentralizing powers, it is essential to ensure the systematic nature of legislation and to strengthen the research and formulation of laws for regional environmental collaborative legislation to ensure that the laws are targeted and operable. “Legislative principles are significant norms for legislative bodies to engage in legislative activities and represent the inherent spirit and character of legislation” [40]. It is necessary to establish fundamental principles and standards for cross-regional environmental protection to reduce the differences in environmental laws and regulations across vertical levels, to ensure consistency and coherence among relevant laws and regulations at different levels, and to avoid legislative conflicts and duplications. Particularly, issues of non-cooperation across vertical hierarchies, which may manifest as objections to environmental permits, loopholes in environmental regulation, and citizen non-compliance with environmental policies [41], may exist. Therefore, it is necessary to perfect the legislative process, including extensively soliciting opinions from all parties, scientifically assessing the effects of legislation, etc., to enhance the scientific nature and transparency of legislation, and to unify, coordinate, and connect relevant environmental laws and regulations.

In terms of the specific content of the exercise of legislative power, focusing on the narrow-sense of regional environmental collaborative legislation based on the current issues of loose legislative structure and insufficient supply of regional environmental collaborative legislation, providing a general foundation for the broad-sense of regional environmental collaborative legislation is prioritized.

5. Discussion

Building upon existing research, this study conducted both quantitative and qualitative analyses. The quantitative analysis collected regional environmental collaborative legislation documents from the three major regions of China: the Three Northeast Provinces, the Yangtze River Delta, and the Beijing—Tianjin—Hebei region. Using balanced panel data from 299 prefecture-level cities in China from 2010 to 2019, a DID model was constructed to empirically test the impact of regional environmental collaborative legislation on the emission of environmental pollutants in prefecture-level cities. In addition, a qualitative analysis was conducted to examine the challenges faced by China’s regional environmental collaborative legislation model in practice. Based on these analyses, policy recommendations for optimization were proposed.

5.1. Discussion on Quantitative Analysis

This study manually collected regional environmental collaborative legislation documents from the three major regions of China: the Three Northeast Provinces, the Yangtze River Delta, and the Beijing—Tianjin—Hebei region. Based on this, balanced panel data from 299 prefecture-level cities in China from 2010 to 2019 were utilized to construct a DID model to empirically test the impact of regional environmental collaborative legislation on the emission of environmental pollutants in prefecture-level cities. By examining how local governments promote the formation and implementation of inter-regional environmental collaborative legislation, and through discussing the economic impact of this environmental policy on urban pollution emissions, this study aims to advance existing research. According to the empirical research results, the implementation of regional environmental collaborative legislation effectively inhibits the discharge of wastewater and sulfur dioxide emissions in prefecture-level cities, indicating significant environmental governance effects of this policy, which is consistent with the evidence obtained in the existing literature. Zhang and Shang (2018), using a coupling assessment model, found that China’s regional environmental collaborative governance has a strong effect on pollutant reduction [22]. Xin et al. (2024) employed a synthetic control method to discuss the impact of regional coordinated environmental policies on pollutant emission reduction in the Beijing—Tianjin—Hebei region and found that these policies effectively reduce atmospheric pollutant emissions in the region [42]. Unlike the aforementioned literature, this study employs a DID model to empirically test the environmental governance effects of regional environmental collaborative legislation in the three major regions of China. This not only examines the economic impact of regional environmental collaborative legislation on urban pollution emissions on a larger geographical scale, but it also provides richer quantitative evidence for examining the policy effects of regional environmental collaborative legislation obtained in existing research methods.

5.2. Discussion on Qualitative Analysis

This paper systematically introduces the current regional environmental collaborative legislation model adopted by the Chinese government in response to regional environmental challenges. It examines the challenges faced by this model in practice, including issues related to localism, legislative authority allocation, and conflicts and coordination between collaborative legislation and existing local environmental legislation. As a result, policy recommendations are proposed, emphasizing the establishment of cooperative mechanisms, coordination among stakeholders, and distribution of local legislative authority. Compared to the existing literature, this study makes several new contributions. Firstly, it addresses the lack of analysis on governance challenges faced by unitary states like China in addressing regional environmental issues. The existing literature predominantly focuses on discussions regarding the coordination issues between federal and state governments in federal systems like those in the United States, neglecting research on policies for regional environmental collaboration in highly centralized unitary states. For instance, Stewart (1977) discussed the challenges faced by federal states in implementing environmental policies [6]. Fisch (2018) compared the advantages and disadvantages of federal and unitary states in executing environmental policies but does not introduce the latest regional environmental collaborative legislation model adopted by China [1]. Secondly, this study provides valuable policy recommendations for optimizing cooperation among local governments of the same rank through legislative models for environmental governance. The existing research mainly discusses the power struggle between higher and lower ranking governments regarding environmental regulation, while overlooking discussions on environmental cooperation among governments of the same rank. For example, Adler (2020) proposed resolving conflicts between federal and local governments regarding environmental jurisdiction but did not provide research concerning the cooperation and challenges in environmental governance policies among local governments of the same rank [3].

5.3. Limitations and Directions for Future Research

This paper holds certain limitations in both quantitative analysis and qualitative aspects.

In terms of quantitative analysis, we utilized city-level data from China spanning the years between 2010 to 2019 and employed a DID model to empirically test the environmental governance effects of regional environmental collaborative legislation. Therefore, this paper exclusively discusses the policy impacts of regional environmental collaborative legislation within the context of China. Due to significant differences among countries in regards to legislative models and environmental governance, the research conclusions obtained in this paper can only support the specific scenario of China. Future research should explore the topic from a broader international perspective, considering the backgrounds of multiple countries. Additionally, while this paper employed a DID model as the empirical research method, the conclusions derived from using a single quantitative research method still possess uncertainties, to some extent. Hence, future research can employ more scientifically rigorous quantitative analysis methods to analyze the subject, ensuring that the positive policy impacts of regional environmental collaborative legislation on environmental pollution control become a consensus in the existing research.

In terms of qualitative analysis, we analyzed the challenges facing China’s regional environmental collaborative legislation and proposed policy recommendations. However, this study only focused on the difficulties encountered by China’s regional environmental collaborative legislation, without delving into the challenges faced by environmental federalism governance models predominant in other countries. This limitation suggests that the research material in this paper may not be comprehensive enough. Future studies could compare regional environmental collaborative governance models in other countries to provide more international comparative examples for addressing regional environmental issues. Additionally, the policy recommendations in this paper mainly discuss collaboration issues among local governments of the same rank, lacking an observation from a macro perspective at the central government level. Therefore, future research could include an analysis of the functions of and roles played by the central government in facilitating collaboration among local governments of the same rank, thereby offering a more comprehensive research perspective for optimizing the regional environmental collaborative legislation.

6. Conclusions

This paper focuses on the regional environmental collaborative legislative system of China, as the largest unitary state, aiming to evaluate the effectiveness of this system through qualitative research and to examine the practical challenges through qualitative analysis, thereby providing beneficial institutional recommendations. Initially, the paper examines the collaborative legislative models of the three most representative regions in China, summarizing that the regional environmental collaborative legislative system is characterized by voluntary cooperation among local governments, with collaborative legal texts serving as action guidelines. Subsequently, to assess the effectiveness of the impact of regional environmental collaborative legislation on environmental governance, the paper conducts empirical testing using balanced panel data from 299 prefecture-level cities in China from 2010 to 2019, constructing a DID model, and finding a significant inhibitory effect of regional environmental collaborative legislation on pollution emissions at the city level. Specifically, the implementation of regional environmental collaborative legislation results in a 19.7% reduction in prefecture-level wastewater emissions and a 26.6% reduction in sulfur dioxide emissions. Finally, to optimize this beneficial mechanism and enhance environmental governance, the paper investigates the challenges faced by regional environmental collaborative legislation, such as localism, difficulties in local legislative authority allocation, and inadequate cooperation mechanisms among local governments of the same rank. It also proposes policy recommendations, such as building a cooperation platform, coordinating the interests of stakeholders, and improving the distribution mechanism of environmental legislative power.