Many uncertainties can be found in the delineation of the external limit of the continental shelf under Art. 76 of the United Nations Convention on the Law of the Sea (UNCLOS), insofar as it refers to the geological notion of the continental margin (so-called extended continental shelf). In any case, today this definition is reflected in customary international law and is confirmed by, inter alia, decisions of the International Court of Justice. It thus applies also to UNCLOS non-party States. However, what has become customary international law is a global regime of ocean spaces that has a coherent logic and includes both the seabed within national jurisdiction, subject to the sovereign rights of the coastal State, and the seabed beyond national jurisdiction (so-called Area), subject to the different regime of common heritage of mankind. Also UNCLOS non-party States that are willing to avail themselves of the right to benefit from an extended continental shelf are bound to have its outer limit determined according to a procedure involving the Commission on the Limits of the Continental Shelf (CLCS) and to make payments and contributions through the International Seabed Authority. By announcing in 2023 the outer limits of its extended continental shelf and by declaring itself prepared to present a submission to the CLCS, the United States – a non-party to the UNCLOS – implicitly agreed on the comprehensive regime for the seabed established by the UNCLOS.
