Outside of the English speaking nations the concept of the TERRITORIAL SEA is one of the most commonly misunderstood or ignored concepts of international law. The issues going on now with China's refusal to abide by the United Nations Law of the Sea Convention UNCLOS) where it concerns territorial seas which are sovereign territory of the adjacent coastal state, and the collection of various agreed to servitudes that make up Outer Continental Shelf (OCS) waters and Exclusive Economic Zone (EEZ) waters is just the latest example of how this concept has not yet achieved universal acceptance despite the large number of nations that signed the UNCLOS convention and the number like the United States that are still not signatory but generally compliant.
For the maritime professional, the concept of the "territorial sea"versus the "high seas" is the single most important concept in international law. Policing the territorial sea of the United States is the daily concern of the U.S. Coast Guard. Challenging the extension of the territorial seas of other nations into the commons of the "high seas"is the daily concern of the U.S. and allied navies. The territorial sea is a primary concept relative to the enduring principles of the international law of territory as it applies to water areas.
THE TERRITORIAL SEA DEFINED:
The territorial sea is a portion of the seas within a definite maritime belt immediately adjacent to a state's coastline. The territorial sea is seaward of, and does not include ports, road-steads, rivers,most bays, some gulfs, straits, or sounds. Most coastal lakes, bays, and sounds and similar waters are not part of the territorial sea but rather are a part of a state's "internal waters". On internal waters a state exercises complete sovereignty identical to its powers over its land areas. Included in this sovereignty over internal waters is the power to completely exclude foreign ships. The territorial sea, by contrast, is subject to some international servitudes.
CONTENTION AT THE BOUNDARIES:
There is widespread international agreement on definitions, rights, and duties relative to the high seas and the territorial seas. The big bone of contention is the breadth of the territorial seas. There seems to be widespread agreement that the breath of the territorial sea is at least 3 miles. There is fairly widespread support in the international community for United Nations Convention On The Law Of The Sea (UNCLOS) definition of the territorial seas subject to certain exceptions at 12 miles , assuming free navigation of international straits is assured, and boundaries between coastal states separated by narrow seas are subject to negotiated or arbitrated settlement.
A few states still claim as their territorial sea as much as 200 miles off their coastlines. China is currently claiming parts of the sea as much as 930 miles from her nearest coast and less than 130 miles from her neighboring states and well within their UNCLOS recognized Exclusive Economic Zones. China is not alone in advocating a virtual closed sea, but is the only nation to do so without so much as a nod to the provisions of UNCLOS. By contrast Russia is using provisions of existing UNCLOS and OCS law to claim all of the Arctic Ocean as an extension of its own Continental Shelf. Russia's latest claim was turned down by the UN on the basis of insufficient scientific information. If Russia is ever successful in its arguments it would not win the Arctic Ocean as a territorial sea.