Maritime Law: UNCLOS and the Rules of the High Seas

The Constitution of the Oceans

In 1982, after nine years of negotiations involving more than 150 countries, the United Nations Convention on the Law of the Sea (UNCLOS) was opened for signature in Montego Bay, Jamaica. Comprising 320 articles and nine annexes, it is the most comprehensive international treaty ever negotiated and is routinely called the "constitution for the oceans." It entered into force on November 16, 1994, and today has 168 state parties. The United States signed UNCLOS but the Senate has never ratified it — yet the US treats most of its provisions as binding customary international law and bases its freedom of navigation operations on UNCLOS norms.

UNCLOS replaced a fragmented system of customary rules with a comprehensive framework governing everything from the width of territorial seas to deep seabed mining rights. The oceans cover 71% of Earth's surface and carry approximately 90% of world trade by volume. Their legal governance is not a peripheral matter.

The Maritime Zone System

UNCLOS divides ocean space into distinct legal zones, each with different rights and obligations for coastal states and other nations. The zones are measured from a baseline — normally the low-water line along the coast.

Innocent Passage and Freedom of Navigation

The right of innocent passage through the territorial sea allows foreign ships to pass continuously, expeditiously, and without stopping through a coastal state's territorial sea. Passage is innocent as long as it is not prejudicial to the peace, good order, or security of the coastal state. UNCLOS Article 19 lists 12 categories of non-innocent passage, including threat or use of force, weapons exercises, spying, propaganda, and launching or landing aircraft.

The EEZ is frequently misunderstood. Coastal states have sovereign rights over resources in the EEZ but not sovereignty itself. Foreign military vessels retain the right to navigate and conduct military activities — including intelligence gathering — in another state's EEZ without permission. China's position, contested by the US and most maritime law scholars, is that foreign military vessels require Chinese permission to conduct military activities in China's EEZ. US freedom of navigation operations (FONOPs) are partly designed to challenge this interpretation.

Dispute Settlement: Three Forums

UNCLOS provides multiple forums for resolving maritime disputes, creating a complex choice-of-forum system.

• International Tribunal for the Law of the Sea (ITLOS): A permanent court established by UNCLOS Annex VI, based in Hamburg. Has jurisdiction over all disputes concerning interpretation or application of UNCLOS unless parties have chosen another forum. Has issued important provisional measures rulings, including in the Arctic Sunrise case (Netherlands v. Russia, 2013).
• International Court of Justice: States may choose the ICJ for UNCLOS disputes if both parties agree.
• Annex VII Arbitration: A compulsory mechanism — states cannot refuse it for disputes falling under UNCLOS — constituted on a case-by-case basis. Has been used extensively, including in the landmark South China Sea case.

The South China Sea Arbitration

In 2016, an Annex VII arbitral tribunal issued its award in the Philippines v. China case, the most significant international ruling on the South China Sea dispute. The Philippines had challenged China's "nine-dash line" claim — a historically derived claim encompassing approximately 90% of the South China Sea — on the grounds that it was inconsistent with UNCLOS.

The tribunal ruled unanimously that China's nine-dash line claim had no legal basis under UNCLOS. It further found that China had violated the Philippines' sovereign rights in its EEZ by interfering with Philippine fishing and oil exploration, and that China's construction of artificial islands on submerged features did not generate territorial sea entitlements. China rejected the award entirely, calling it "null and void," and has not modified its behavior in the South China Sea. The award stands as an authoritative legal ruling that one major party treats as non-existent. The gap between legal clarity and enforcement is stark.

Piracy and Universal Jurisdiction

UNCLOS Article 101 defines piracy as any illegal acts of violence, detention, or depredation committed for private ends by the crew or passengers of a private ship or aircraft against another ship or aircraft on the high seas. The definition is technically narrow — it excludes acts committed for political purposes and acts in territorial waters (which are crimes under domestic law, not UNCLOS piracy).

Piracy is subject to universal jurisdiction under Article 105: any state may seize pirate ships and arrest pirates on the high seas and try them in its courts, regardless of the nationality of the pirates or the flag of the vessel. The Somali piracy crisis of 2008–2012, which saw over 1,000 hostages held and an estimated $5–7 billion in costs to global shipping annually, led to the largest multinational naval counter-piracy operation since World War II and significant development of piracy prosecution frameworks in Kenya, Seychelles, and other regional states.

The Deep Seabed: Common Heritage and Mining

The area beyond national jurisdiction — the deep seabed and its resources — is declared by UNCLOS to be the "common heritage of mankind." No state may claim sovereignty over the area or its resources. The International Seabed Authority (ISA), established by UNCLOS and headquartered in Kingston, Jamaica, controls deep seabed mining through a licensing system. By 2024, the ISA had issued over 30 exploration licenses to states and sponsored entities covering polymetallic nodules, cobalt-rich crusts, and seafloor massive sulfides.

The commercial exploitation regime remains contested. Developing states, which were promised technology transfer and revenue sharing under the original UNCLOS deal, argue the ISA has been captured by wealthy states and mining corporations. Environmental scientists warn that deep seabed mining will cause irreversible damage to little-understood ecosystems. A 2021 "two-year rule" triggered by Nauru on behalf of a sponsored contractor created deadline pressure for the ISA to finalize mining regulations — a process still ongoing as of 2024 without resolution. The seabed holds trillions of dollars in minerals. How they are extracted, or whether they should be extracted at all, is one of the defining resource conflicts of the coming decades.