Cross-border marine governance innovation and challenges under asymmetric legal frameworks in the Guangdong-Macao in-depth cooperation zone

Cross-border marine governance in contexts where distinct legal systems coexist within a single sovereign state presents challenges that conventional transnational governance models cannot resolve. This paper examines the Guangdong-Macao In-Depth Cooperation Zone in Hengqin as a critical case of institutional innovation under the constitutional framework of “One Country, Two Systems.” Drawing on publicly available policy documents, regulatory texts, and official reports spanning September 2021 to April 2026, the paper develops a three-dimensional analytical framework encompassing legislative authority, policy content, and implementation logic to assess how asymmetric legal structures shape governance outcomes. The analysis documents two institutional innovations introduced in Hengqin: a dual-director co-governance architecture that establishes a formal platform for equal decision-making between Guangdong Province and the Macao Special Administrative Region (SAR), and a “soft law first, hard law consolidation” strategy that enables progressive rule alignment while respecting legislative autonomy. The paper finds that these innovations have achieved measurable progress in joint water quality monitoring, coastal ecological restoration, coordinated maritime patrols, and cross-border emergency response coordination. At the same time, it identifies persistent structural constraints: the cooperation zone possesses limited independent legislative power, a decision-execution disjuncture concentrates authority at provincial and SAR levels while implementation responsibility falls on municipal agencies, a critical governance gap exists in the domain of area-based marine conservation measures, and complete rule alignment remains structurally unattainable while the two legal systems remain independent. The paper proposes actionable recommendations organized around activating shared economic incentives, developing a differentiated rule alignment taxonomy, addressing the marine protected area governance gap through OECM-based approaches, and strengthening vertical coordination across levels of government. The Hengqin case demonstrates how polycentric governance can function across distinct legal orders through appropriate interface mechanisms. These findings may offer useful references for other coastal contexts where distinct legal systems must be coordinated within a single sovereign space.