Law of the Sea — the Maritime Zones — Public International Law Notes

Law of the Sea — the Maritime Zones

In 1951, in the Anglo-Norwegian Fisheries case, Britain challenged the way Norway drew straight lines across its jagged coast to claim more sea. The ICJ upheld Norway’s straight baselines. That case, and the long codification that followed, ended in the master treaty of the sea — UNCLOS 1982 — which fixes exactly how far out each zone runs. Learn the zones as a ladder marching outward from the shore, and every sea problem becomes a question of “which rung is the ship on?”

The maritime zones — a ladder outward from the coast

Sovereignty does not stop at the water’s edge; it fades outward through a series of belts, each conferring less authority than the last. The measuring starts from the baseline (normally the low-water line, or straight baselines across a deeply indented coast — Anglo-Norwegian Fisheries, 1951). Work outward.

A. Internal waters

Waters landward of the baseline (ports, bays, rivers). The coastal State has full sovereignty, as over land; there is no right of innocent passage here.

B. Territorial sea (maritime belt) — up to 12 nautical miles

A belt of sea adjacent to the coast, up to 12 nm from the baseline (Art. 3 UNCLOS). The coastal State has sovereignty over the water, seabed, subsoil and airspace — subject to the right of innocent passage of foreign ships (passage that is not prejudicial to the peace, good order or security of the coastal State). Over foreign merchant ships the coastal State may exercise criminal jurisdiction in defined cases (Art. 27 UNCLOS); warships are immune.

C. Contiguous zone — up to 24 nautical miles

A zone beyond the territorial sea, up to 24 nm from the baseline (Art. 33 UNCLOS). Here the coastal State does not have sovereignty — only limited enforcement powers to prevent and punish breaches of its customs, fiscal, immigration and sanitary (health) laws committed in its territory or territorial sea.

Article 33, UNCLOS (1982): in a contiguous zone not extending beyond 24 nm from the baseline, the coastal State may exercise the control necessary to prevent and punish infringement of its customs, fiscal, immigration or sanitary laws within its territory or territorial sea.

D. Exclusive Economic Zone (EEZ) — up to 200 nautical miles

A zone up to 200 nm from the baseline (Arts. 55–57 UNCLOS). The coastal State has sovereign rights over the natural resources (living and non-living) of the water, seabed and subsoil — exploration, exploitation, conservation and management — and jurisdiction over artificial islands and marine research. But other States keep the high-seas freedoms of navigation, overflight and the laying of cables. It is not territorial sea and not high seas — it is a special resource zone.

E. Continental shelf — 200 nm (up to 350 nm)

The seabed and subsoil beyond the territorial sea to the outer edge of the continental margin, or 200 nm, and up to 350 nm where the margin extends (Arts. 76–77 UNCLOS). The coastal State has sovereign rights over the seabed resources (minerals, oil, sedentary species). These rights exist ipso facto and ab initio — they do not depend on occupation or proclamation (North Sea Continental Shelf, 1969).

F. High seas — beyond national jurisdiction

All parts of the sea beyond the EEZ (Arts. 86–90 UNCLOS). The high seas are open to all States and belong to none (res communis). The freedoms of the high seas are: navigation, overflight, laying submarine cables and pipelines, constructing artificial islands, fishing, and scientific research. Ships are subject to the exclusive jurisdiction of their flag State. Two problem-generating rules live here:

Hot pursuit (Art. 111 UNCLOS) — if a foreign ship breaches the coastal State’s laws in its internal waters, territorial sea, contiguous zone or EEZ, the coastal State may pursue it onto the high seas and arrest it, provided the pursuit begins within the zone, is continuous and uninterrupted, and stops once the ship enters another State’s territorial sea.

Article 111, UNCLOS (1982): the hot pursuit of a foreign ship may be undertaken when the coastal State has good reason to believe the ship has violated its laws; it must begin while the ship is within the pursuing State’s waters/zone and may continue onto the high seas only if not interrupted; it ceases as soon as the ship enters the territorial sea of its own or a third State.

On collisions, contrast Article 97 UNCLOS (1982), which (reversing Lotus) gives penal jurisdiction over a high-seas collision only to the flag State or the State of the accused’s nationality.
Piracy and universal jurisdiction — any State may seize a pirate ship on the high seas.

G. Inter-oceanic canals

Man-made waterways joining two seas (Suez, Panama, Kiel) that pass through a State’s territory. They are under the territorial sovereignty of that State, but by treaty are kept open to the ships of all nations in peace and war (e.g. the Constantinople Convention 1888 for Suez).

Article 3, UNCLOS (1982): “Every State has the right to establish the breadth of its territorial sea up to a limit not exceeding 12 nautical miles, measured from baselines determined in accordance with this Convention.”

In Simple Terms: Picture five rungs going out to sea. Rung 1 (territorial sea, 12 nm): the State owns it, but foreign ships may pass innocently. Rung 2 (contiguous zone, 24 nm): no ownership, just power to enforce customs/immigration/health/tax rules. Rung 3 (EEZ, 200 nm): the State owns the resources but not the water for navigation. Rung 4 (continental shelf): the State owns the seabed resources, automatically. Rung 5 (high seas): nobody owns it; everyone is free, and each ship answers to its flag State.

⚠️ DON’T CONFUSE — territorial sea vs contiguous zone vs EEZ

Territorial sea (12 nm): the coastal State has full sovereignty (subject to innocent passage). Contiguous zone (24 nm): no sovereignty — only limited enforcement of customs, fiscal, immigration and sanitary laws. EEZ (200 nm): no general sovereignty — only sovereign rights over resources; other States keep navigation and overflight. Trap: students treat the EEZ as if it were territorial sea (so foreigners “cannot enter”) — wrong; foreigners may navigate and overfly the EEZ freely, they just may not take its resources.

🧩 WORKED EXAMPLE — foreign fishermen in the EEZ

Facts. Fishermen of State X fish in the EEZ of neighbouring State Y. Y stops them. X argues its fishermen may fish anywhere beyond Y’s territorial sea.

Rule. In the EEZ (Arts. 55–57 UNCLOS) the coastal State has sovereign rights over living resources; only navigation/overflight freedoms survive for others.

Apply. The decoy is “EEZ is not territorial sea, so it must be high seas”. False — the EEZ is a resource zone. Fishing is a resource activity reserved to Y. X’s fishermen may sail through Y’s EEZ but may not fish in it without Y’s permission.

Conclusion. Y was entitled to stop them; X’s argument confuses freedom of navigation with a right to the zone’s resources.

flowchart TD
    A["Baseline (low-water line)"]
    A --> B["Internal waters<br/>full sovereignty, no innocent passage"]
    B --> C["Territorial sea 12 nm<br/>sovereignty + innocent passage"]
    C --> D["Contiguous zone 24 nm<br/>enforce customs/fiscal/immigration/health"]
    D --> E["EEZ 200 nm<br/>sovereign rights over resources"]
    E --> F["Continental shelf (to 350 nm)<br/>seabed resources"]
    F --> G["High seas<br/>free to all; flag-State jurisdiction; hot pursuit Art. 111"]
    classDef box fill:#e8f0fe,stroke:#333,color:#111;
    class A,B,C,D,E,F,G box;

Case Laws

Anglo-Norwegian Fisheries Case (UK v. Norway, 1951, ICJ) — straight baselines drawn along a deeply indented coast are valid; baselines need not follow the low-water line slavishly.
North Sea Continental Shelf Cases (1969, ICJ) — continental-shelf rights exist ipso facto and ab initio; delimitation is governed by equitable principles, not the equidistance rule as custom.
The Corfu Channel Case (1949, ICJ) — States have a right of innocent passage for warships through straits used for international navigation.

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