From fragmentation to conditional coordination: China Coast Guard environmental enforcement under ecological codification and the BBNJ Agreement

China’s consolidated maritime enforcement system connects dispersed domestic powers with new obligations under the Ecological and Environmental Code (EEC) and the Biodiversity Beyond National Jurisdiction (BBNJ) Agreement. This study examines the relationship between China’s implementation responsibility and the legality of a specified China Coast Guard (CCG) measure. Five analytical inquiries distinguish institutional competence, applicable requirements, legal consequences, measure-specific authority, and international jurisdiction across three legal domains. They develop established legality review by pairing its measure-specific conclusion with a diagnosis of the implementation task that remains. Controlled variations show how the same rejection of boarding can correspond to referral, a necessary domestic implementing instrument, or procedural completion. Alternative routes are assessed against the applicable obligation’s addressee, required legal effect, timing, and mandatory procedures. For activities involving foreign-flagged vessels, Chinese incorporation identifies a personal nexus but must be connected to the corporation’s role in the particular activity. A proposed operational-control criterion examines executable decision powers over initiation, continuation, or environmentally material aspects of that activity. The framework distinguishes established, unresolved, absent and inapplicable requirements and links proposed implementation routes to administrative follow-up, operator responses and verification.