Overview
A foreign ship and the people on it are under two legal systems at once: the law of the flag state and the law of the coastal state whose waters or port the ship is in. The master must know when the coastal state may act against the ship (inspection, detention, arrest) and against the crew (investigation, arrest, prosecution), and what to do when local officials come on board.
After this lesson you will be able to:
- Explain where a coastal state has jurisdiction, from internal waters to the high seas.
- Distinguish flag, port and coastal state roles.
- Describe civil, administrative and criminal jurisdiction over a foreign ship.
- State the rights and risks of crew members who are arrested, detained or accused.
- Explain the limits of coastal state power, including innocent passage and immunity of state ships.
- Act correctly as master or officer when local authorities board the ship.
How the rules developed
For centuries the law of the sea was based on the freedom of the seas. National rights were limited to a narrow belt of water along the coast, usually three nautical miles, based on the "cannon shot" rule attributed to Cornelius Bynkershoek. Pressure to extend national claims grew in the 20th century, to reach minerals and fish stocks and to control pollution.
| Date | Event |
|---|---|
| 17th century | Freedom of the seas, with a coastal belt of about three nautical miles ("cannon shot" rule). |
| 1930 | League of Nations conference at The Hague fails to agree on the breadth of the territorial sea. |
| 1945 | President Truman extends US control to the natural resources of its continental shelf. Other states follow. |
| 1946–1950 | Argentina, Chile, Peru and Ecuador claim 200 nautical miles to cover their Humboldt Current fishing grounds. |
| 1958 | UNCLOS I produces four Geneva conventions but leaves the breadth of the territorial sea unsettled. |
| 1967 | Only 25 states still use the three-mile limit; 66 use 12 miles and eight claim 200 miles. |
| 1973–1982 | UNCLOS III. The Convention is adopted in 1982. |
| 16 November 1994 | The Convention enters into force, one year after Guyana became the 60th state to ratify. |
Zones and the three states
Coastal state power gets weaker as a ship moves away from land. The zones follow the UN Convention on the Law of the Sea 1982 (UNCLOS):
| Zone | Extent | Coastal state authority over foreign ships and crew |
|---|---|---|
| Internal waters (ports, harbours, bays, rivers) | Landward of the baseline | Full sovereignty. Local criminal, civil and administrative law applies. Entry needs the state's consent, except in force majeure. |
| Territorial sea | Up to 12 nautical miles | Sovereignty, subject to the right of innocent passage (Arts. 2, 3, 17). Limited jurisdiction over a ship only passing through. |
| Contiguous zone | Up to 24 nautical miles | Control to prevent and punish breaches of customs, fiscal, immigration and sanitary laws (Art. 33). |
| Exclusive economic zone | Up to 200 nautical miles | Sovereign rights over resources and protection of the marine environment (Arts. 56, 220). No general jurisdiction. |
| High seas | Beyond the EEZ | Flag state has exclusive jurisdiction (Art. 92). |
Port State Control officers check foreign ships against the main conventions: SOLAS 1974 (Ch. I, Reg. 19), MARPOL 73/78 (Art. 5(2)), STCW 1978 (Art. X), the Load Lines Convention 1966 (Art. 21) and MLC 2006.
The interactive diagrams and knowledge check below work through the zones, the three kinds of jurisdiction, crew rights on arrest, and the key UNCLOS limits — Articles 27, 28, 32, 92, 97, 218 and 230.