waters, territorial, all waters within the jurisdiction, recognized in international law, of a country. Certain waters by their situation are controlled by one nation; these include wholly enclosed inland seas, lakes, and rivers. Control of boundary lakes and rivers extends to the middle of the navigable channel, but agreements to share the use of such waters and of waters that flow through several countries (e.g., the Rhine, the Danube) are common. When waters are almost completely bordered by one country, but lie along an international navigation route (e.g., the Bosporus), treaties often make them available to all ships.
Since the 18th cent. coastal states have been held to have jurisdiction over unenclosed waters for 3 nautical mi (3.45 mi/5.55 km) from the low water line, a measure originally derived from the distance of a cannon shot. In the case of a bay up to 24 mi (39 km) wide, a line drawn from one enclosing point to the other marked the outer limit of territorial jurisdiction. A broader zone of jurisdiction to combat smuggling has long been claimed by various states, as by the United States during prohibition.
Merchant ships of all flags have the right of "innocent passage" in a nation's territorial waters; the rights of nonbelligerent foreign warships in this zone, and the extent of the jurisdiction of the coastal nation's courts over ships passing through and incidents in the zone, have long been matters of debate. Fishing and mineral extraction within the zone are entirely within the control of the coastal nation. In the 20th cent., coastal nations progressively widened their claims over offshore waters, especially in the face of competition from foreign fishing fleets and in anticipation of rich oil, gas, and mineral finds on the continental shelf. The UN-sponsored Law of the Sea treaty, which went into effect in 1994, codified territorial waters of 12 nautical mi (13.8 mi/22.2 km) and an exclusive economic zone of 200 nautical mi (230 mi/370 km). In 1999, U.S. agencies were empowered by presidential proclamation to enforce American law up to 24 miles (39 km) offshore, doubling the previous limit.