In the international law of the sea, human activities in the ocean are regulated according to multiple jurisdictional zones. Thus, the spatial distribution of jurisdiction of States is the foundation of the law of the sea. Where the jurisdiction of two or more coastal States overlaps, delimitation of the overlapping marine spaces is at issue. This chapter will deal with rules of international law with regard to maritime delimitation, focusing mainly on the following issues: (1) the cardinal principle applicable to maritime delimitations, (2) the three-stage approach and its limitations, (3) relevant circumstances in the law of maritime delimitation, (4) the delimitation of the continental shelf beyond 200 nautical miles, and (5) the role of international courts and tribunals in the development of the law of maritime delimitations.

UNCLOS carries various obligations relating to protection of the marine environment. States must take positive action to meet those obligations, going beyond reduction of pollution. Special protection must be afforded to vulnerable ecosystems, and this can involve the establishment of marine protected areas. The international community has committed to adoption of the ecosystem approach in various soft law instruments and it has, particularly come to feature in legal instruments of ocean management. Indeed, the future of the oceans depends on application of the ecosystem approach.

The judicial process of maritime delimitation is clearly established, and it pays little regard to ecological circumstances. However, a majority of maritime boundaries is negotiated, and States are free to depart from traditional judicial methods when agreeing on bilateral arrangements. An ecosystem approach to maritime delimitation could promote sustainable development and biodiversity within national jurisdiction, and even mitigate the adverse effects of climate change on the marine environment. It could provide a better basis for resource management and be an improvement on the sectoral approach.

This chapter introduces the conceptual framework of delimitation methodology. It reviews the sources of the law of maritime delimitation applicable to the delimitation of the continental shelf beyond 200 nm. More specifically, it examines the elements of delimitation methodology and the formulations of delimitation methodology that evolve over time. On that basis, this chapter raises the methodological questions to be addressed in the delimitation of the continental shelf beyond 200 nm and develops the approach for their analysis, which goes beyond the prevailing three-stage approach established in the jurisprudence since the 2009 Black Sea case.