The United Nations Convention on the Law of the Sea is the principal multilateral treaty governing the rights and responsibilities of states in the world's oceans. It was opened for signature on 10 December 1982 in Montego Bay, Jamaica, and entered into force on 16 November 1994, one year after the 60th ratification. As of the mid-2020s it has more than 165 parties, including the European Union; notable non-parties include the United States, which signs onto most provisions as customary international law but has never ratified due to objections (later partly addressed by the 1994 Implementation Agreement on Part XI concerning deep-seabed mining).
UNCLOS codifies and develops earlier Geneva Conventions of 1958. Key zones it establishes include:
- Territorial sea of up to 12 nautical miles, where coastal state sovereignty applies subject to innocent passage.
- Contiguous zone of up to 24 nm for limited enforcement.
- Exclusive Economic Zone (EEZ) of up to 200 nm, granting sovereign rights over living and non-living resources.
- Continental shelf, extendable beyond 200 nm subject to recommendations from the Commission on the Limits of the Continental Shelf (CLCS).
- High seas and the Area (the seabed beyond national jurisdiction), declared the "common heritage of mankind" and administered by the International Seabed Authority (ISA) in Kingston, Jamaica.
The Convention created three institutions: the International Tribunal for the Law of the Sea (ITLOS) in Hamburg, the ISA, and the CLCS. Disputes can also go to the ICJ or Annex VII arbitration, as in the 2016 South China Sea Arbitration (Philippines v. China), where the tribunal rejected China's nine-dash line claims.
In June 2023, states adopted the BBNJ Agreement (treaty on Biodiversity Beyond National Jurisdiction) under UNCLOS to govern marine genetic resources and high-seas marine protected areas.
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In 2016, an Annex VII arbitral tribunal constituted under UNCLOS ruled in favor of the Philippines against China's nine-dash line claims in the South China Sea.