Created: 18 February 2025
The ocean covers more than 70% of the Earth’s surface, yet for most of human history, it had almost no rules. Nations claimed whatever parts they could control, leading to fights over fishing, trade routes, and resources. To bring order to the seas, the world eventually came together to write a “constitution for the oceans” — the United Nations Convention on the Law of the Sea (UNCLOS).
The Origins:
The concept of “freedom of the seas” dates back to the 1600s, when Dutch jurist Hugo Grotius argued that the sea should be open to all, thereby establishing the idea of “freedom of the seas.” But as coastal states began to exploit marine resources and protect their interests, this principle proved too simple.
By the mid-20th century, disputes were erupting over fishing rights, oil exploration, and navigation routes. The UN organized three major conferences to fix this:
- UNCLOS I (1958) – Produced four Geneva Conventions on the territorial sea and contiguous zone, the high seas, the continental shelf, and fishing and conservation of living resources of the high seas.
- UNCLOS II (1960) – Focused on fixing a single rule for territorial sea and fisheries limits, but ended without agreement and produced no new convention.
- UNCLOS III (1973–1982) – Developed the 1982 UNCLOS. It entered into force on 16 November 1994, 12 months after the date of deposit of the sixtieth instrument of ratification [1] and established the modern law of the sea framework.
Today, over 160 countries are parties to UNCLOS, making it one of the most widely accepted international agreements.
Maritime Zones: Rights, Powers, and Limits
UNCLOS divides the ocean into zones measured from coastal baselines, the low-water line along the coast. [2] Each has different rights and obligations.
- Internal Waters – The waters landward of the baseline, such as rivers, bays, and harbors, are subject to the coastal state sovereignty, equivalent to its land territory. Foreign ships have no right of passage unless consent is granted.[3]
- Archipelagic Waters – Archipelagic States may draw straight baselines joining the outermost points of their islands, enclosing archipelagic waters within.[4] While sovereignty is exercised over these waters, it is constitutionally constrained by mandatory navigational regimes, including innocent passage and archipelagic sea lanes passage. These waters are therefore not equivalent to internal waters.[5]
- Territorial Sea – Extending up to 12 nautical miles from the baseline, the territorial sea is subject to coastal State sovereignty [6] exercised subject to the right of innocent passage for foreign ships. Passage must be continuous, expeditious, and non-prejudicial to the peace, good order, or security of the coastal State.[7]
- Contiguous Zone – The contiguous zone extends up to 24 nautical miles from the baseline. Here, the coastal State may exercise control necessary to prevent or punish violations of its customs, fiscal, immigration, or sanitary laws committed within its territory or territorial sea.[8]
- Exclusive Economic Zone (EEZ) – the area beyond and adjacent to the territorial sea up to 200 NM, where the coastal State enjoys sovereign rights for the purpose of exploring, exploiting, conserving, and managing natural resources.[9] Other States retain freedoms of navigation and overflight, subject to the duty of due regard for the coastal State’s rights.[10]
- Continental Shelf – The continental shelf comprises the seabed and subsoil extending to 200 nautical miles, and in some cases up to 350 nautical miles, where the seabed is a natural prolongation of the land territory.[11] Coastal State rights over the shelf are exclusive and inherent, but do not affect the legal status of the waters above.[12]
- The High Seas – Beyond national jurisdiction lie the high seas, open to all States. Freedoms of navigation, fishing, scientific research, and cable-laying apply, subject to international law and the obligation to use the seas for peaceful purposes.[13]
Maritime Features and Legal Entitlements
A coastal State’s maritime entitlements depend on the legal status of the maritime features. Under UNCLOS, these features are classified, and each has distinct entitlements, as follows:
- Islands – Naturally formed land above water at high tide that can sustain human habitation or an intrinsic economic life. It generates the full set of maritime zones.[14]
- Rocks – Features above water at high tide that cannot sustain human habitation or economic life. Rock may generate a territorial sea, but no EEZ or continental shelf.[15]
- Low-Tide Elevations – Features exposed at low tide but submerged at high tide generate no maritime zones of their own, though they may serve as baselines in limited circumstances.[16]
- Submerged Features – Permanently submerged banks or reefs form part of the seabed and generate no maritime entitlements.[17]
- Artificial Islands – Man-made structures do not possess island status and generate no maritime zones, though safety zones of up to 500 meters may be established.[18]
Rights of Passage: Balancing Freedom of Navigation and Sovereignty
UNCLOS protects global mobility through carefully defined passage regimes:
- Innocent Passage – Applies in the territorial sea, archipelagic waters, and international straits used for navigation. It may be regulated for safety, environmental protection, and security, and may be temporarily suspended in limited circumstances, except in designated archipelagic sea lanes.[19]
- Transit Passage – Applies in straits used for international navigation. It allows continuous and expeditious transit in normal modes of operation and may not be suspended.[20]
- Archipelagic Sea Lanes Passage – Allows ships and aircraft to transit designated routes through archipelagic waters in normal modes of operation. This right may not be suspended or effectively impaired.[21]
Dispute Resolution Mechanisms
UNCLOS establishes a comprehensive system for the peaceful settlement of disputes concerning its interpretation or application. States may choose among:
- International Tribunal for the Law of the Sea – A specialized judicial body created under UNCLOS with jurisdiction over a wide range of law of the sea disputes, including prompt release of vessels and crews, provisional measures, and certain seabed-related matters.
- International Court of Justice – The principal judicial organ of the United Nations, competent to hear inter-State disputes that may include issues arising under UNCLOS when the parties have accepted its jurisdiction.
- Arbitration under Annex VII – A flexible and widely used process where ad hoc tribunals resolve disputes. Annex VII arbitration acts as the default mechanism when no mutual choice is made for the forum.
- Special Arbitration under Annex VIII – A procedure designed for technically complex disputes, such as those concerning fisheries, marine scientific research, marine pollution, or navigation and related facilities.[22]
This system operates subject to limited optional exceptions, including for certain military activities and maritime boundary disputes.[23] It has nonetheless produced landmark rulings, including the 2016 South China Sea Arbitration.
Why UNCLOS Matters Today
UNCLOS is more than a set of lines on a map. It is the rulebook that explains how the oceans are meant to be used, by navies, governments, industries, and ordinary seafarers alike. It sets the legal boundaries for naval operations, resource use, environmental protection, and how dangerous incidents at sea should be handled.
As new challenges emerge, from deep-sea mining and autonomous vessels to growing competition between States, UNCLOS continues to provide the common legal reference point that helps prevent confusion, miscalculation, and conflict.
At its core, UNCLOS answers three practical questions that matter at sea: who is allowed to act, where they may do so, and under what legal authority. For States, navies, industry, and policymakers, it remains an essential guide for keeping the oceans orderly, stable, and governed by law rather than power alone.
Footnotes
[1] United Nations Convention on the Law of the Sea art. 308, Dec. 10, 1982, 1833 U.N.T.S. 397 (entered into force Nov. 16, 1994) [hereinafter UNCLOS].
[2] UNCLOS, supra note 1, art. 5.
[3] Id., art. 8.
[4] Id., art. 47.
[5] Id., arts. 49–53.
[6] Id., art. 3.
[7] Id., art. 19.
[8] Id., art. 33.
[9] Id., art. 56.
[10] Id., art. 58.
[11] Id., art. 76.
[12] Id., art. 78.
[13] Id., arts. 87, 88.
[14] Id., art. 121(1)– (2).
[15] Id., art. 121(3).
[16] Id., art. 13.
[17] Id., arts. 13, 76.
[18] Id., art. 60(8).
[19] Id., arts. 17–26, 45, 52.
[20] Id., arts. 37–44.
[21] Id., arts. 53–54.
[22] Id., arts. 287, Annexes VII–VIII.
[23] Id., art. 298.