Legal Definitions - territorial sea

The territorial sea refers to a belt of coastal waters extending up to 12 nautical miles from a state's baseline (typically the low-water line along its coast). Within this zone, the coastal state exercises full sovereignty, meaning it has complete control over the air space above, the seabed below, and the waters themselves. This sovereignty is similar to that exercised over its land territory, subject only to the right of "innocent passage" for foreign vessels.

Here are some examples illustrating the concept of the territorial sea:

• Example 1: Environmental Protection

  Imagine a large cargo ship that suffers an engine failure and begins to discharge pollutants into the ocean just 7 nautical miles off the coast of a small island nation. Because this incident occurs within the island nation's 12-nautical-mile territorial sea, the nation has the full legal authority to respond. It can immediately deploy its own resources for cleanup, impose significant fines on the shipping company, and take legal action against the vessel's owners for environmental damage, just as it would if the spill occurred on its land territory.

• Example 2: Naval Passage and Security

  A research vessel from Country A plans to sail through the waters directly off the coast of Country B to reach a specific research site. Country B's territorial sea extends 12 nautical miles from its shore. While Country B has full sovereignty over these waters, international law grants Country A's vessel the right of innocent passage. This means the vessel can transit through as long as its passage is continuous, expeditious, and not harmful to the peace, good order, or security of Country B. Country B cannot arbitrarily deny this passage but can enforce regulations related to safety, navigation, and environmental protection.

• Example 3: Law Enforcement and Customs

  A coast guard patrol from Country C detects a small, fast boat entering its waters just 5 nautical miles from its coastline, heading directly towards a secluded bay known for smuggling activities. Because the boat is well within Country C's territorial sea, the coast guard has the immediate right to intercept, board, and investigate the vessel. If the boat is found to be carrying illegal contraband or engaging in unauthorized entry, Country C can arrest the crew, seize the vessel, and prosecute them under its national laws, exercising its full sovereign power over its territorial waters.