Flexible interpretation and strategic interaction of the “not undermine” clause: a case study of the BBNJ agreement

The "not undermine" clause in the BBNJ Agreement stands an innovation for reconciling relations with the existing marine governance. However, its ambiguous wording may lead to interpretive divergences and potential conflicts. With the Agreement now in force, the practical effect of this clause no longer depends solely on the text itself; rather, subject to the rules of treaty interpretation, it will be jointly shaped by the strategic interactions among the Conference of the Parties, potential parties, and dispute settlement bodies within an institutional framework. To anticipate its implementation pathway, this paper develops a tripartite game model, analyzing the distinct strategic choices and equilibrium outcomes of the above three actors in interpreting the "not undermine" clause. The findings are as follows: (1) phased implementation is an important pathway for optimizing the clause’s effectiveness. In the early stage following entry into force, cautious application and transitional arrangements can facilitate broad participation; once membership size and institutional authority stabilize, the operational content of the clause can be progressively elaborated through subsequent practice, technical guidance, and coordination mechanisms. (2) The leading role of key countries carries greater weight than merely increasing the number of state parties. By leveraging their inherent strengths to exercise differentiated leadership, key countries can effectively amplify the Agreement’s influence. (3) Where multiple plausible interpretive approaches exist, the institutional costs faced by dispute settlement bodies affect the degree to which different interpretive orientations are acceptable. While the analysis primarily serves the implementation of the BBNJ Agreement, the framework’s insights into multi-actor interaction, interpretive flexibility, and institutional coordination also offer methodological reference for other ocean conservation regimes that contain similar “not undermine” clauses.