Law of the sea (UNCLOS)

The constitutional framework of the oceans

The United Nations Convention on the Law of the Sea (UNCLOS), adopted at Montego Bay on 10 December 1982 and entered into force on 16 November 1994, is the codifying treaty for ocean governance. It superseded the four 1958 Geneva Conventions and is frequently called the 'constitution for the oceans'. With 169 parties (including the European Union) as of 2024, much of it now reflects customary international law binding even non-parties such as the United States, which signs but has not ratified it owing to Senate objections to Part XI on deep seabed mining.

The graduated maritime zones

UNCLOS measures every zone from the baseline the low-water line along the coast (Article 5), with straight baselines permitted where the coast is deeply indented (Article 7), as the ICJ accepted in the Anglo-Norwegian Fisheries case (1951).

• Internal waters (landward of baselines): full sovereignty; no right of innocent passage.
• Territorial sea up to 12 nautical miles (Article 3): full sovereignty subject to the right of innocent passage (Articles 17 to 19), which is suspended if passage is prejudicial to peace, good order or security.
• Contiguous zone up to 24 nm (Article 33): the coastal state may enforce customs, fiscal, immigration and sanitary laws.
• Exclusive Economic Zone (EEZ) up to 200 nm (Articles 55 to 57): sovereign rights over living and non-living resources, but the EEZ is not territory other states retain freedoms of navigation and overflight (Article 58).
• Continental shelf to 200 nm, extendable to 350 nm or 100 nm beyond the 2,500-metre isobath on submissions to the Commission on the Limits of the Continental Shelf (Article 76).
• High seas (Article 87): freedoms of navigation, overflight, fishing and cable-laying, governed by the principle of the freedom of the seas (Grotius, Mare Liberum, 1609).
• The Area the seabed beyond national jurisdiction is the common heritage of mankind (Article 136), administered by the International Seabed Authority in Kingston.

Passage regimes a candidate must distinguish

Three navigation regimes recur in exams. Innocent passage applies in the territorial sea; submarines must navigate surfaced and show their flag (Article 20). Transit passage applies through straits used for international navigation, such as the Strait of Hormuz or the Strait of Gibraltar (Articles 37 to 38), and cannot be suspended. Archipelagic sea lanes passage (Article 53) applies through archipelagic states such as Indonesia and the Philippines. Conflating these three is a common error; retain that transit passage is more permissive than innocent passage and is non-suspendable.

Dispute settlement under Part XV

UNCLOS contains a compulsory dispute-settlement system (Part XV, Articles 286 to 296). On ratification a state chooses one or more fora under Article 287: the International Tribunal for the Law of the Sea (ITLOS) in Hamburg, the International Court of Justice, an Annex VII arbitral tribunal, or an Annex VIII special arbitral tribunal. Where parties have not chosen the same forum, Annex VII arbitration is the default. Article 298 permits states to exclude maritime boundary delimitation, military activities and law-enforcement disputes by declaration China, Russia and India have lodged such declarations.

The landmark cases

The South China Sea Arbitration (Philippines v. China), decided by an Annex VII tribunal at The Hague on 12 July 2016, is the single most testable case. The tribunal held that China's 'nine-dash line' had no legal basis insofar as it claimed historic rights beyond UNCLOS entitlements; that none of the Spratly features generated a 200 nm EEZ because under Article 121(3) rocks which cannot sustain human habitation or economic life of their own have only a 12 nm territorial sea; and that China's island-building violated its environmental obligations under Articles 192 and 194. China refused to participate or comply, illustrating the limits of enforcement.

For maritime delimitation, retain the three-stage equidistance/relevant-circumstances method confirmed in Romania v. Ukraine (Black Sea), ICJ, 3 February 2009: draw a provisional equidistance line, adjust for relevant circumstances, then check disproportionality. The Bangladesh v. Myanmar case (ITLOS, 14 March 2012) the tribunal's first maritime boundary delimitation applied this method and recognised Bangladesh's continental shelf beyond 200 nm. India and Bangladesh resolved their maritime boundary by Annex VII arbitration on 7 July 2014, with India accepting an award largely favourable to Bangladesh, a model of peaceful settlement India invokes diplomatically.

India and the BBNJ Agreement

India ratified UNCLOS on 29 June 1995 and enacted the Maritime Zones Act, 1976. The newest instrument is the BBNJ Agreement (Biodiversity Beyond National Jurisdiction), adopted on 19 June 2023 under UNCLOS, creating marine protected areas on the high seas and an access-and-benefit-sharing regime for marine genetic resources. It requires 60 ratifications to enter into force watch its progress as a current-affairs hook.

Why this matters for the exam

UNCLOS sits at the intersection of static law and live geopolitics, which is exactly why examiners across the shared layer return to it. In UPSC GS-2 it appears under 'important international institutions' and 'effect of policies of developed and developing countries on India's interests', typically framed through the Indo-Pacific, the South China Sea and freedom-of-navigation operations. The 2017 PYQ on the South China Sea and the 2021 question on the Indo-Pacific construct both required a candidate to deploy UNCLOS zones and the 2016 award as analytical scaffolding rather than mere description.

How it is tested

The FSOT tests UNCLOS in the World History/Geography and the U.S. interests components, including the United States' non-party status and its reliance on customary navigation freedoms to justify FONOPs in the South China Sea. The CSS International Law paper and BCS international-relations sections demand precise recall of zone breadths, Article numbers and the innocent-versus-transit passage distinction.

High-yield facts to retain

• Territorial sea 12 nm; contiguous zone 24 nm; EEZ 200 nm; shelf to 350 nm (Articles 3, 33, 57, 76).
• Article 121(3): rocks unable to sustain habitation get no EEZ the decisive holding in the 2016 award.
• Transit passage (Article 38) is non-suspendable; innocent passage (Article 25) can be suspended temporarily.
• The Area is the common heritage of mankind (Article 136); the ISA administers it.
• Default dispute forum under Annex VII; Article 298 opt-outs for boundary/military disputes.
• BBNJ Agreement adopted 19 June 2023.

The analytical move examiners reward

Strong answers connect doctrine to enforcement realities: the 2016 award was legally binding under Article 296 yet unenforced because UNCLOS has no police power, so compliance rests on reputational and coalitional pressure. A candidate who writes that UNCLOS 'settled' the South China Sea misreads it; the law is clear, but power determines compliance. Pair the legal entitlement with the geopolitical incentive and the answer reads like an analyst's, not a textbook's.