After the second world war, the International Court of Justice decided two contentious cases: Corfu Channel (1949), which addressed straits used for international navigation; and Fisheries (1951), which considered baselines marking the start of the territorial sea. Both were initiated by the United Kingdom after two other states, Albania and Norway respectively, tried to prevent British vessels from operating without permission in their coastal waters - warships in one case, trawlers in the other. Taken together, the decisions set out the parameters of the modern approach to the law of the sea: preserving the naval powers’ traditional freedoms of navigation while recognising the coastal states’ claims to resources in the waters off their coasts.

The law of the sea, one of the oldest areas of international law, is now substantially codified in the 1982 United Nations Convention on the Law of the Sea (‘UNCLOS’), the ‘constitution for the oceans’. UNCLOS ushered in the modern law of the sea, providing a comprehensive regime for maritime zones, navigational rights and freedoms, fishing and other uses of the world’s oceans that cover approximately 70% of the Earth’s surface. As an island country with extensive maritime zones, Australia has a major stake in the law of the sea and has been actively involved in its development and implementation. Australia was one of the original signatories to UNCLOS and ratified it in 1994, the year it entered into force generally. The central issues of concern for the law of the sea have traditionally been the extent of maritime jurisdiction and navigational rights. However, a much broader range of matters is addressed in contemporary law and practice, from sustainable fisheries management through to mining of the deep seabed beyond national jurisdiction. There are also major new challenges on the horizon – none more so than climate change.

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.

Where the maritime claims of adjacent or opposite coastal states overlap with one another, a potential maritime boundary exists. Thanks to the extensions of maritime claims offshore, the number of potential maritime boundaries has substantially increased and only around half of potential maritime boundaries have been even partially settled. The role of technology in the evolution of maritime boundary delimitation is outlined. Emerging technologies, especially space-based infrastructure, are explored and found to have an increasingly important role to play in the determination of the location of the land/sea interface at the coast and thus the baselines from which equidistance lines are calculated as well as in terms of positioning technologies, allowing the realization of a coherent global geodetic reference system. The role of emerging technologies in the context of maritime boundary dispute resolution is also considered.