The seaward limits of each jurisdictional zone are measured from baselines. Thus, rules concerning baselines are of particular importance in the law of the sea. In particular, rules governing straight baselines and bays merit serious consideration. Furthermore, attention must be devoted to the legal status of islands and low-tide elevations because the existence of these maritime features may affect the seaward limits of marine spaces under national jurisdiction. Against that background, this chapter will address rules concerning baselines and related issues, focusing mainly on the following questions: (1) the rules governing baselines, (2) the problems associated with rules with regard to straight baselines, (3) the rules governing juridical bays in international law, (4) historic bay, (5) the definition of an island, and (6) the differences between islands, rocks and low-tide elevations.

This chapter examines UNCLOS tribunals’ contribution to the development of the law on maritime entitlement and maritime delimitation-two distinct but related concepts. The chapter first analyses and assesses the extent to which UNCLOS tribunals—as the first international tribunals to deal with questions relating to the entitlement to a continental shelf beyond 200 nm and entitlement from insular features—have contributed to clarifying the legal ambiguities concerning these two issues. The chapter then analyses UNCLOS tribunals’ decisions relating to maritime delimitation within and beyond 200 nm, with a focus on examining the convergences and divergences in UNCLOS tribunals’ application of the established three-stage approach within 200 nm and on assessing the contribution of UNCLOS tribunals to clarifying the legal ambiguities concerning the delimitation of the continental shelf beyond 200 nm.