The Law of the Seas is a branch of international law concerned with public order at sea.  The United Nations Convention on the Law of the Sea (UNCLOS) represents an attempt to codify international law regarding territorial waters, sea-lanes, and ocean resources.  The UNCLOS is described as a “constitution for the oceans.”  The Law of the Sea Convention defines the rights and responsibilities of nations in their use of the world’s oceans, establishing guidelines for businesses, the environment, and the management of marine natural resources.

The UNCLOS replaces the older ‘freedom of the seas’ concept.  As per the freedom of seas concept, national rights were limited to a specified belt of water extending from a nation’s coastlines, usually three nautical miles.  All waters beyond national boundaries were considered international waters — free to all nations, but belonging to none of them.  The UNCLOS set the limit of various areas, measured from a carefully defined baseline.

According to UNCLOS:

• The coastal state is free to set laws, regulate use, and use any resource regarding its internal waters.  Foreign vessels have no right of passage within internal waters.  Internal waters Covers all water and waterways on the landward side of the baseline.
• Each country’s sovereign territorial waters extend to a maximum of 12 nautical miles (22 km) beyond its coast.  Foreign vessels are granted the right of innocent passage through this zone.
• Beyond territorial waters, every coastal country may establish an exclusive economic zone (EEZ) extending 200 nautical miles (370 km) from shore.  Within the EEZ the coastal state has the right to exploit and regulate fisheries, construct artificial islands and installations, use the zone for other economic purposes (e.g., the generation of energy from waves), and regulate scientific research by foreign vessels.  Otherwise, foreign vessels (and aircraft) are entitled to move freely through (and over) the zone.
• With regard to the seabed beyond territorial waters, every coastal country has exclusive rights to the oil, gas, and other resources in the seabed up to 200 nautical miles from shore  or to the outer edge of the continental margin, whichever is the further.  The extension of this areas is subjected to an overall limit of 350 nautical miles (650 km) from the coast or 100 nautical miles (185 km) beyond the 2,500-meters isobaths (a line connecting equal points of water depth).  This area is known as the continental shelf, though it differs considerably from the geological definition of the continental shelf.  Where the territorial waters, EEZs, or continental shelves of neighboring countries overlap, a boundary line is drawn by agreement to achieve an equitable solution.  When the countries are not able to reach agreement, the boundary has been determined by the International Court of Justice or by an arbitration tribunal.
• The high seas lie beyond the zones described above.  The waters and airspace of this area are open to use by all countries, except for those activities prohibited by international law (e.g., the testing of nuclear weapons.)