Marine Protected Areas (MPAs) are specifically designated zones of restricted human activity, based on ecological, biological, or socioeconomic factors. Since the adoption of the United Nations Convention on the Law of the Sea (UNCLOS) in December 1982, states and international organisations have increasingly utilised the MPAs as a tool for environmental protection. A number of MPAs are now found in the Exclusive Economic Zones (EEZ) of states and on the high seas; whereas previously, MPAs were rarely designated beyond the territorial sea. Both EEZs and high seas MPAs introduce restrictions on human activities such as fishing, shipping, scientific research, vessel discharges and waste dumping.

This thesis examines the changing balance of the law of the sea, demonstrated through the development of MPAs and restrictive measures of the sort identified above. By delving into the law and politics of designation and management of MPA regimes, this thesis conducts a comparative analysis of MPA regimes. This thesis argues that the MPA regimes are the implementation of the environmental obligations under UNCLOS and states’ active interpretation of international law to expand environmental interests. This expansion is observed in the law and practice of MPA regimes, on how the regimes circumvent or overcome their legal limitations and endeavour to induce state participation. This thesis concludes that the environmental interests shown through the MPA regimes are tipping the balance of interests in the law of the sea.

This thesis is a doctrinal exploration of five MPA regimes. The five MPA regimes include two situated exclusively within the EEZs of states and three on the high seas. In the EEZ, the International Maritime Organization’s Particularly Sensitive Sea Areas, and the Helsinki Commission’s Baltic Sea MPAs are examined. On the high seas, the 1980 Convention on the Conservation of Antarctic Marine Living Resource MPAs, the International Seabed Authority’s Areas of Particular Environmental Interests, and MPAs under the 1992 Convention for the Protection of the Marine Environment of the North-East Atlantic are studied.