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The United Nations Convention on the Law of the Sea, opened for signature at Montego Bay on 10 December 1982 and in force since 16 November 1994, is the foundational treaty of modern maritime law. It defines the maritime zones a coastal state may claim, the rights of navigation across them, freedom of the high seas, the deep seabed regime, and the framework for maritime boundary disputes. As of 2025 it has 168 state parties. The United States has not ratified but recognises the navigation and boundary provisions as customary international law.
Full coastal-state sovereignty — no right of innocent passage. Foreign vessels enter only with the coastal state's consent (which is granted expressly, or impliedly by port opening for international trade). Nationals of the coastal state may board and enforce law without qualification.
Full coastal-state sovereignty, subject only to the right of innocent passage for foreign vessels. The coastal state may exercise complete criminal + civil jurisdiction over foreign vessels but must not hamper innocent passage. Innocent means not prejudicial to the peace, good order, or security of the coastal state — Article 19 enumerates specific non-innocent activities (weapons exercises, spying, propaganda, launching aircraft, fishing, wilful pollution, research not authorised).
Beyond the 12 nm territorial sea. Coastal state may exercise limited enforcement for customs, fiscal, immigration, and sanitary matters. Cannot exercise general jurisdiction. Useful for anti-smuggling and quarantine.
Coastal state has sovereign rights over living + non-living resources of the water column and seabed, and over energy production. Freedom of navigation, overflight, and cable-laying preserved for other states. Not sovereignty in the full sense — foreign vessels have significant rights on the water surface, but not to fish, extract, or research without consent.
Coastal state has sovereign rights over the seabed and subsoil (including oil, gas, and sedentary species). Rights extend beyond the EEZ where the natural prolongation of the continental margin extends further. Extended-continental-shelf claims are reviewed by the Commission on the Limits of the Continental Shelf (CLCS).
All parts of the sea not in any state's territorial sea, EEZ, or archipelagic waters. Freedom of the high seas for all — navigation, overflight, cable-laying, artificial installations, fishing, scientific research. Vessel subject only to the jurisdiction of its flag state (with limited exceptions: piracy, slave trade, unauthorised broadcasting, ships without nationality, right of hot pursuit).
Regulated by the International Seabed Authority (ISA), based in Kingston, Jamaica. Common heritage of mankind. Mining licences require ISA authorisation. Recent controversy over deep-sea polymetallic-nodule mining licensing.
Article 17 grants innocent-passage right to all ships. Passage must be continuous and expeditious. Submarines must transit surfaced flying their flag. Coastal states may adopt laws relating to safety of navigation, cables, fisheries, pollution — but cannot suspend passage without a specific security necessity notified to the IMO.
Article 38: in straits connecting two parts of the high seas or EEZ, all ships and aircraft have the right of transit passage — a stronger right than innocent passage. Submarines may transit submerged. Overflight is permitted (unlike innocent passage). Coastal states cannot suspend transit passage. Applies to Hormuz, Bab-el-Mandeb, Gibraltar, Malacca, Dover, and other major straits.
Article 53: in archipelagic states (e.g. Indonesia, Philippines, Fiji), the archipelagic state may designate sea lanes and traffic separation schemes for international navigation. Ships have a right similar to transit passage through these designated lanes.
Article 101 defines piracy as illegal acts of violence or detention, or any act of depredation, committed for private ends by the crew or passengers of a private ship, and directed on the high seas against another ship or against persons or property on board such other ship. Every state may seize a pirate ship on the high seas and prosecute in its own courts (Article 105). This universal jurisdiction is the basis for anti-piracy operations off Somalia + the Gulf of Aden. Cross-reference /piracy-incidents.
Note the limits: Article 101 requires (a) private ends, (b) high seas or place outside coastal jurisdiction, (c) two-ship element (attacker vessel + attacked vessel). Political attacks (e.g. Houthi missile strikes on merchant vessels, which come from land installations and are politically motivated) do NOT meet the UNCLOS piracy definition. The Sea Shepherd anti-whaling actions ARE arguably piracy under some interpretations.
When a coastal state detains a foreign vessel for violation of its laws (typically fisheries or pollution), UNCLOS Article 292 requires the coastal state to promptly release the vessel and crew upon posting of a reasonable bond. Disputes about the reasonableness of the bond can be brought to the International Tribunal for the Law of the Sea (ITLOS) in Hamburg. Recent examples: Camouco (2000), Monte Confurco (2000), Volga (2002).
UNCLOS Part XV establishes a compulsory dispute-settlement regime. State parties choose forum:
Notable cases: Philippines v China (2016) South China Sea arbitration (Annex VII); Guyana v Suriname (2007); the Enrica Lexie (Italy v India, 2020).
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