Interaction of Treaty and Custom in the Concept of Offshore Archipelagos

This paper discusses whether claims to close off the waters of so-called 'offshore archipelagos' by non-archipelagic states are consistent with international law against the background of the relationship (and potential entanglement) between treaty and custom. First, it discusses the term ‘archipelagos’ and ‘archipelagic state’ in international law and traces its development and status before the 1982 Law of the Sea Convention (LOSC). The paper then turns to the regulation of archipelagic states, and their rights and obligations, in the LOSC, against the background of the travaux preparatoires—ie the discussion in the Third United Nations Conference on the Law of the Sea. We argue that the analysis demonstrates quite clearly that there is no basis for claiming rights accruing to an archipelagic state for non-archipelagic states that have sovereignty over one or more offshore archipelagos. This sets the stage for a discussion of possible arguments for ‘going beyond the LOSC’ and seeking to argue on the basis of customary international law, or, more timidly, practice. Hence, the paper addresses the relationship between treaty and custom and the argument that the question at hand is actually not regulated by the LOSC and remains subject to customary international law. Then, the paper discusses whether there is an argument that subsequent practice may have established the agreement of the parties that the relevant provisions of the LOSC are to be interpreted as allowing their invocation by non-archipelagic states with offshore archipelagos. Finally, the paper considers a potential argument regarding ‘supervening custom’, ie customary law that may have emerged since the adoption of the LOSC and that permits such claims by non-archipelagic states. We conclude that there is no basis for arguing that non-archipelagic states are able to claim any sort of special status for 'offshore archipelagos'.