NOAA Office of General Counsel International Section, Marine Zones and Boundaries

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MARITIME ZONES AND BOUNDARIES


Zones and Boundaries image.
Photo 69: Maritime Zones
(NOAA Coastal Services Center)

The maritime zones recognized under international law include internal waters, the territorial sea, the contiguous zone, the exclusive economic zone, the continental shelf, the high seas and the Area. With the exception of the high seas and the Area, each of these maritime zones is measured from the baseline determined in accordance with customary international law as reflected in the 1982 Law of the Sea Convention.

The limits of these zones are officially depicted on NOAA nautical charts. The limits shown on the most recent chart edition takes precedence. For a description of the various U.S. maritime zones, as well as the Three Nautical Mile Line and Natural Resource Boundary, see the NOAA Coast Pilot (Chapter 1 in each volume) or review the information available on NOAA's link to download limits of the U.S. Digital Maritime Zones/Boundaries (source information for the NOAA nautical charts.)

The boundaries of these maritime zones between coastal nations are established through international agreements entered into by those nations. For the official description of the U.S. maritime boundaries with other nations contact the U.S. Department of State.

Additional reference information:Some of these links are to external sites.

Baseline

Generally speaking, the normal baseline is the low-water line along the coast as marked on large-scale charts officially recognized by the coastal State. Special rules for determining the baseline apply in a variety of circumstances, such as with bays, ports, mouths of rivers, deeply indented coastlines, fringing reefs, and roadsteads. Consistent with these rules, the U.S. baselines are the mean of the lower low tides as depicted on the largest scale NOAA nautical charts. The U.S. normal baselines are ambulatory and subject to changes as the coastline accretes and erodes.


Internal Waters

Internal waters are the waters (for example, bays and rivers) on the landward side of the baseline from which the breadth of the territorial sea is measured. Each coastal State has full sovereignty over its internal waters as if they were part of its land territory. The right of innocent passage does not apply in internal waters.


Territorial Sea

Each coastal State may claim a territorial sea that extends seaward up to 12 nautical miles (nm) from its baselines. The coastal State exercises sovereignty over its territorial sea, the air space above it, and the seabed and subsoil beneath it. Foreign flag ships enjoy the right of innocent passage while transiting the territorial sea subject to laws and regulations adopted by the coastal State that are in conformity with the Law of the Sea Convention and other rules of international law relating to such passage.

The U.S. claimed a 12 nm territorial sea in 1988 (Presidential Proclamation No. 5928, December 27, 1988).

Additional reference information:Some of these links are to external sites.

  • Letter to Certain Foreign Ministers of November 8, 1793 proclaiming a three-mile Territorial Sea of the United States (cannon shot rule)
  • Proclamation 5928 of December 27, 1988. Territorial Sea of the United States of America. (54 Fed. Reg. 777 (Jan. 9, 1989)).
  • Office of Legal Counsel, U.S. Department of Justice, "Legal Issues Raised by Proposed Presidential Proclamation to Extend the Territorial Sea" (Oct. 4, 1988)
  • Testimony of Rear Admiral Joseph Vorbach, Chief Counsel, U.S. Coast Guard, before the Subcommittee on Oceanography and the Great Lakes of the House Committee on Merchant Marine and Fisheries regarding the extension of the U.S. territorial sea from 3 to 12 miles (March 21, 1989).
  • USSR – U.S.: Joint Statement with attached Uniform Interpretation of Rules of International Law Governing Innocent Passage (Wyoming, 1989)

Contiguous Zone

Each coastal State may claim a contiguous zone adjacent to and beyond its territorial sea that extends seaward up to 24 nm from its baselines. In its contiguous zone, a coastal State may exercise the control necessary to prevent the infringement of its customs, fiscal, immigration or sanitary laws and regulations within its territory or territorial sea, and punish infringement of those laws and regulations committed within its territory or territorial sea. Additionally, in order to control trafficking in archaeological and historical objects found at sea, a coastal State may presume that their removal from the seabed of the contiguous zone without its consent is unlawful.

In 1972, the U.S. proclaimed a contiguous zone extending from 3 to 12 miles offshore (Department of State Public Notice 358, 37 Fed. Reg. 11906 (June 15, 1972), consistent with the 1958 UN Convention on the Territorial Sea and Contiguous Zone. In 1999, eleven years after President Reagan extended the U.S. territorial sea to 12 miles, President Clinton proclaimed a contiguous zone extending from 12 to 24 nm offshore (Presidential Proclamation No. 7219, August 2, 1999), consistent with Article 33 of the Law of the Sea Convention.

Additional reference information:Some of these links are to external sites.


Exclusive Economic Zone

US EEZ limits from Global Perspective.
Photo 36: US EEZ limits from Global Perspective
(NOAA Office of Coast Survey)

Each coastal State may claim an Exclusive Economic Zone (EEZ) beyond and adjacent to its territorial sea that extends seaward up to 200 nm from its baselines (or out to a maritime boundary with another coastal State). Within its EEZ, a coastal State has: (a) sovereign rights for the purpose of exploring, exploiting, conserving and managing natural resources, whether living or nonliving, of the seabed and subsoil and the superjacent waters and with regard to other activities for the economic exploitation and exploration of the zone, such as the production of energy from the water, currents and winds; (b) jurisdiction as provided for in international law with regard to the establishment and use of artificial islands, installations, and structures, marine scientific research, and the protection and preservation of the marine environment, and (c) other rights and duties provided for under international law.

The U.S. claimed a 200 nm EEZ in 1983 (Presidential Proclamation No. 5030 of March 10, 1983). The U.S. EEZ overlaps its 12 nm - 24 nm contiguous zone.

Note: Under certain U.S. fisheries laws, such as the Magnuson-Stevens Fishery Conservation and Management Act, the term EEZ is defined as having an inner boundary that is coterminous with the seaward (or outer) boundary of each of the coastal states of the U.S. See 16 U.S.C. 1802(11). Under the Submerged Lands Act, the seaward boundary of each of the coastal states is generally three nautical (or geographic) miles from the coast line. The seaward boundaries of Florida (Gulf of Mexico coast only), Texas and Puerto Rico extend nine nautical miles from the coast line. In the Great Lakes, each state’s seaward boundary may extend to the international maritime boundary with Canada. See 33 U.S.C. 1312. Under the Submerged Lands Act, a coastal state’s seaward boundary can be fixed by Supreme Court decree. (See below for further information on the Three Nautical Mile Line and the Natural Resources Boundary.)

Additional reference information:Some of these links are to external sites.

Three Nautical Mile Line

The Three Nautical Mile Line, as measured from the territorial sea baseline and previously identified as the outer limit of the U.S. territorial sea, is retained on NOAA charts because it continues to be used in certain federal laws.

Note: Since the "coast line," a term used in the Submerged Lands Act, 43 U.S.C. 1301 et seq., and the baseline are determined using the same criteria under international law, the Three Nautical Mile Line is generally the same as the seaward boundaries of the coastal states of the United States under the Submerged Lands Act. There are exceptions; therefore, the Three Nautical Mile Line does not necessarily depict the seaward boundaries of states under the Submerged Lands Act.


Natural Resources Boundary

The nine (9) nautical mile Natural Resources Boundary is the seaward limit of the submerged lands of Puerto Rico, Texas and the Gulf coast of Florida. It coincides with the inner limit of the outer continental shelf under the Outer Continental Shelf Lands Act.


Continental Shelf

Maritime Zones and Boundaries, including limits of territorial sea, continguous zone, EEZ and continental shelf.
Photo 70: Maritime Zones and Boundaries, including limits of territorial sea, contiguous zone, EEZ and continental shelf.
(NOAA Coastal Services Center)

Each coastal State has a continental shelf that is comprised of the seabed and subsoil of the submarine areas that extend beyond its territorial sea throughout the natural prolongation of its land territory to the outer edge of the continental margin, or to a distance of 200 nm from its baselines where the outer edge of the continental margin does not extend up to that distance (or out to a maritime boundary with another coastal State).

Wherever the outer edge of a coastal State's continental margin extends beyond 200 nm from its baselines, it may establish the outer limit of its continental shelf in accordance with Article 76 of the UN Convention on the Law of the Sea. The portion of a coastal State's continental shelf that lies beyond the 200 nm limit is often called the extended continental shelf.

A coastal State has sovereign rights and exclusive jurisdiction over its continental shelf for the purpose of exploring it and exploiting its natural resources. The natural resources of the continental shelf consist of the mineral and other non-living resources of the seabed and subsoil together with living organisms belonging to sedentary species, that is to say, organisms which, at the harvestable stage, either are immobile on or under the seabed or are unable to move except in constant physical contact with the seabed or subsoil.

The U.S. has claimed a continental shelf that extends out at least 200 nm (Presidential Proclamation No. 2667 of September 28, 1945 and Presidential Proclamation No. 5030 of March 10, 1983). Since 2001, the U.S. has been engaged in gathering and analyzing data to determine the outer limits of its extended continental shelf.

Additional reference information:Some of these links are to external sites.

High Seas

The high seas are comprised of all parts of the sea that are not included in the exclusive economic zone, in the territorial sea or in the internal waters of a State, or in the archipelagic waters of an archipelagic State.

Waters Forming International Straits

International straits are those areas of overlapping 12 nautical mile territorial seas that connect one area of the high seas or EEZ to another area of the high seas or EEZ and are used for international navigation.  Part III of the Law of the Sea Convention (articles 34-45) describes the regime for transit passage through such straits as well as the rights and jurisdiction of the States bordering it.  Transit passage is the right of a ship or aircraft to transit, pass or navigate through an international strait in a continuous and expeditious manner.  LOSC arts. 37, 38.  Ships in maptransit passage must comply with the duties set forth in LOSC article 39, which include proceeding without delay and refraining from any activities other than those incident to their normal modes of continuous and expeditious transit.  Ships in transit passage may not carry out any research or survey activities without the prior authorization of the States bordering the strait.  LOSC art. 40.  States bordering international straits may designate sea lanes and prescribe traffic separation schemes for navigation where necessary to promote safe passage of ships.  LOSC art. 41.  They may also adopt laws and regulations relating to transit passage in respect of certain activities, such as fishing.  LOSC art. 42.  The transit passage regime does not otherwise affect the legal status of the waters forming an international strait, or the exercise of sovereignty or jurisdiction by the bordering States over the waters, air space, seabed and subsoil of the strait.  LOSC art. 34.

Additional Reference Information:

  • LOSC Part III, Straits Used for International Navigation      
  • Law of the Sea Convention, 1994 Letters of Transmittal and Submittal and Commentary (U.S. Department of State, Dispatch Magazine, Vol. 6, Supp. 1, Feb. 1995)    
  • Proclamation 5928 of December 27, 1988, Territorial Sea of the United States of America (54 Fed. Reg. 777 (Jan. 9, 1989)) (Ships and aircraft of all countries enjoy the right of transit passage through international straits.”)
  • The Corfu Channel Case (United Kingdom v. Albania), 1949 I.C.J. Rep. 4, 28-29 (Judgment of Apr. 9) (International Court of Justice held that the Corfu Channel between mainland Albania and the island of Corfu was a “useful route for international maritime traffic" and belonged to “the class of international highways through which passage cannot be prohibited by a coastal state in time of peace.”)             
  • In re J.W. Westcott Co., 266 F. Supp. 2d 601, 605 (E.D. Mich. 2003) (relying upon LOSC to support a finding that the Detroit River was an international strait)
  • Restatement (Third) of Foreign Relations Law § 513 (1987)

Area

The Area is comprised of the seabed and subsoil beyond the limits of national jurisdiction. It does not include superadjacent waters (i.e., the water column) or the air space above those waters. The Area and its resources are the common heritage of mankind, and no State may claim or exercise sovereignty or sovereign rights over any part of the Area or its resources. LOSC. arts. 1(1), 135-137.


Comparative Sizes of the Various Maritime Zones

Areas of the Earth covered by the Oceans approx. 335.0 million km2
High Seas 200.4 million km2
Territorial Seas 22.4 million km2
Contiguous Zones 6.6 million km2
Exclusive Economic Zones 101.9 million km2
Total areas under national jurisdiction excluding extended continental shelves beyond 200 nm 131.0 million km2

Source: UNEP/GRID-Arendal, Continental Shelf: The Last Maritime Zone (2011) at 28.

As a measure of comparison, the mass of the contiguous United States (all states except Alaska and Hawaii)
is approximately 7.7 million km2 (square kilometers)