Informer: US maritime limits based on UN sea law treaty

By By Andrew Perzo / American Press

How much of the Gulf of Mexico is under United States control? When and how did this happen?

The United States has a say in what happens in 700,000 or so square kilometers of the gulf — roughly the water north of a

line drawn from the mouth of the Rio Grande to the Straits of Florida.

The U.S. government has full

sovereignty over its territorial waters, which extend 12 nautical miles

from a baseline measurement,

which is defined in the United Nations Convention on the Law of

the Sea as “the low-water line along the coast as marked on

large-scale charts officially recognized by the coastal State.”

The official charts, maintained by the

National Oceanic and Atmospheric Administration, identify the baseline

as the “mean

lower low-water line,” or MLLW. The baseline is set by the U.S.

Baseline Committee, which is headed by the U.S. State Department.

The sovereignty in territorial seas

extends to the airspace above the water and to the seabed beneath it. In

territorial waters,

all nations’ vessels, including warships, have the right of

“innocent passage” — i.e., presenting no threat to peace and security

— but are subject to the sovereign nation’s laws.

Additionally, the U.N. convention — a

treaty the U.S. adheres to but hasn’t ratified — recognizes coastal

nations’ right to

exercise some control over a “contiguous zone,” which abuts the

territorial waters and extends an additional 12 nautical miles


In the contiguous zone, the U.S. may prevent and punish “infringement of its customs, fiscal, immigration or sanitary laws

and regulations within its territory or territorial sea,” according to the treaty.

The territorial seas claim, which

includes the waters around Guam, Puerto Rico and the U.S. Virgin

Islands, was made by presidential

proclamation in 1988. The contiguous zone was established by

presidential proclamation in 1999.

The U.N. Law of the Sea Convention also

grants coastal nations the right to set up an exclusive economic zone,

which the United

States established by presidential proclamation in 1983. The EEZ

extends 188 nautical miles from the seaward boundary of the

territorial waters — or 200 nautical miles from the baseline — and

includes the contiguous zone.

“Within the Exclusive Economic Zone,” the proclamation reads, “the United States has ... sovereign rights for the purpose

of exploring, exploiting, conserving and managing natural resources, both living and non-living, of the seabed and subsoil

and superjacent waters and with regard to other activities for the economic exploitation and exploration of the zone, such

as production of energy from the water, currents and winds.”

It also asserts the U.S. government’s

“jurisdiction with regard to the establishment and use of artificial

islands, and installations

and structures having economic purposes, and the protection and

preservation of the marine environment.”

The U.N. treaty allows coastal nations to have jurisdiction over “marine scientific research” in an EEZ, but the presidential

proclamation makes no claim to it.


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The Informer answers questions from readers each Sunday, Monday and Wednesday. It is researched and written by Andrew Perzo, an American Press staff writer. To ask a question, call 494-4098, press 5 and leave voice mail, or email