Maritime Zones and Boundaries
The maritime zones recognized under international law include internal waters, the territorial sea, the contiguous zone, the exclusive economic zone(EEZ), the continental shelf, the high seas and the Area. The breadth of the territorial sea, contiguous zone, and EEZ (and in some cases the continental shelf) is measured from the baseline determined in accordance with customary international law as reflected in the 1982 Law of the Sea Convention offsite link.
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. Maritime Limits & Boundaries (source information for the NOAA nautical charts.)
The boundaries of these maritime zones between coastal States 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:
- U.S. Department of State, Maritime Boundaries
- U.S. Department of State, Limits in the Seas
- CIA World Fact Book summarizes transnational issues including boundary disputes with other nations
- U.S. Maritime Limits & Boundaries NOAA Office of Coast Survey
- NOAA Office of Coast Survey, charting of U.S. Maritime Zones and Boundaries
- Determination of the U.S. National Baseline by Meredith A. Westington and Matthew J. Slagel, Office of Coast Survey, National Ocean Service- NOAA
- Demystifying the Maritime Zones and Other Marine Boundaries on NOAA’s Nautical Charts. Proceedings of the 14th Biennial Coastal Zone Conference, 2005. (paper) and presentation
- Shore and Sea Boundaries. Volumes 1-3 (DOC NOAA, Aaron L. Shallowitz and Mike Reed)
- NOAA (Office of Coast Survey), U.S. Maritime Limits & Boundaries FAQ
- U.S. Department of Defense, Maritime Claims Reference Manual (information on maritime claims of coastal States)
- State Practice in Delimiting Maritime Zones offsite link (a database of the UN Division for Ocean Affairs and Law of the Sea)
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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.
Additional reference information:
- Meredith A. Westington and Matthew J. Slagel, U.S. Maritime Zones and the Determination of the National Baseline offsite link.
Internal (or inland) waters are the waters on the landward side of the baseline from which the breadth of the territorial sea is measured. The coastal State has full sovereignty over its internal waters as if they were part of its land territory. The coastal State may exclude foreign flag vessels from its internal waters subject to the right of entry of vessels in distress. The right of innocent passage does not apply in internal waters. Examples of internal waters include rivers, canals, and lakes, including The Great Lakes.
Additional reference information:
- 1982 United Nations Law of the Sea Convention, Article 8 offsite link
- U.S. v. Louisiana, 394 U.S. 11, 22 (1969) offsite link, (“Under generally accepted principles of international law, the navigable sea is divided into three zones, distinguished by the nature of the control which the contiguous nation can exercise over them. Nearest to the nation’s shores are its inland, or internal waters. These are subject to the complete sovereignty of the nation, as much as if they were a part of its land territory, and the coastal nation has the privilege even to exclude foreign vessels altogether.”)
- United States v. Postal, 589 F.2d 862 (5th Cir. 1979) offsite link, cert. denied, 444 U.S. 832 (1979) offsite link
- Restatement (Second) of Foreign Relations Law § 13 (Internal Waters) (1965)
- 48 C.J.S. International Law § 12 (Inland waters of coastal states or nations) (2021)
- 44B Am. Jur. 2d International Law § 85 (Inland waters) (2021)
- Oxford Public International Law: Internal Waters (2013) offsite link
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 airspace 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:
- Secretary of State Thomas Jefferson, Letter to Certain Foreign Ministers of November 8, 1793 (asserting a provisional territorial sea extending a “distance of one sea-league or three geographical miles from the sea shores”) (cannon shot rule)
- Department of State Public Notice 358, June 1, 1972), 37 Fed. Reg. 11906 (June 15, 1972) (stating the U.S. position that there exists a 3-mile territorial sea off its coast).
- United States v. Maine, 420 U.S. 515 (1975) offsite link (observing that the United States possesses full sovereignty over the marginal seas and the land underlying it extending three geographical miles seaward from the ordinary low water mark)
- U.S. v. Postal, 589 F.2d 862, 869 (5th Cir. 1980) offsite link (citing cases noting that the United States has claimed a 3-nautical mile territorial sea since the earliest days of the Republic)
- Sayre Archie Schwarztrauber, The Three-Mile Limit of Territorial Seas: A Brief History (1972) offsite link
- Proclamation 5928 of December 27, 1988. Territorial Sea of the United States of America, (54 Fed. Reg. 777 (Jan. 9, 1989)), extending the territorial sea from three to 12 nautical miles
- 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).
- Andrew Rosenthal, Reagan Extends Territorial Waters to 12 Miles offsite link, NEW YORK TIMES, Dec. 29, 1988.
- USSR – U.S offsite link.: Joint Statement with attached Uniform Interpretation of Rules of International Law Governing Innocent Passage (Wyoming, 1989)
- INS, Changing Definition of External Boundary of the United States, 57 Fed. Reg. 47257 (Oct. 15, 1992) (amending the regulatory definition of “external boundary” to comport with Presidential Proclamation 5928).
- International Court of Justice, Maritime Delimitation and Territorial Questions between Qatar and Bahrain (Qatar v. Bahrain), 2001 ICJ 40 offsite link (Judgment of 16 March 2001) (all States enjoy the right of innocent passage accorded by customary international law)
- U.S. Department of Defense Annual Freedom of Navigation (FoN) Reports
- Congressional Research Service, Legal Sidebar, Freedom of Navigation and Territorial Seas (May 18, 2015) offsite link
- UN Division for Ocean Affairs and the Law of the Sea, Notifications of Suspension of Innocent Passage offsite link
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:
- Department of State Public Notice 358, June 1, 1972), 37 Fed. Reg. 11906 (June 15, 1972) (establishing a Contiguous Zone extending from 3 nm to 12 nm).
- Presidential Proclamation 7219 of August 2, 1999, Contiguous Zone of the United States. (64 Fed. Reg. 48701 (August 8, 1999)) (extending seaward limit of the Contiguous Zones from 12 to 24 nm from the baseline).
- Correction to Proclamation 7219 (64 Fed. Reg. 49844 (Sept. 14, 1999)).
- Press Release by Vice-President Al Gore, “Extension of Federal Enforcement Zone in U.S. Coastal Waters Will Help Prevent Violations of Environmental, Customs, or Immigration Laws”(Sept. 2, 1999).
- Exchange of Memoranda between the Department of State (1989) and the Department of Justice (1991) on the Extension of the Contiguous Zone to 24 nm.
Exclusive Economic Zone
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 claimed 12 nm – 24 nm contiguous zone. The U.S. generally recognizes claims of foreign nations to an EEZ. See Mayaguezanos por la Salud y el Ambiente v. U.S offsite link., 198 F.3d 297 (1st Cir. 1999); Koru North America v. U.S offsite link., 701 F. Supp. 229, 236 n. 6 (CIT 1988).
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 individual coastal states of the U.S. See 16 U.S.C. § 1802(11) offsite link. Under the Submerged Lands Act, the seaward boundary of each of the individual 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 U.S. state’s seaward boundary may extend to the international maritime boundary with Canada. See 43 U.S.C. § 1312 offsite link. Under the Submerged Lands Act, a coastal state’s seaward boundary may 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:
- Proclamation 5030 of March 10, 1983. Exclusive Economic Zone of the United States. (48 Fed. Reg. 10605 (March 14, 1983)).
- President Ronald Reagan, Statement on United States Ocean Policy, 19 Weekly Comp. Pres. Doc. 383 (March 10, 1983).
- Fact Sheet, United States Ocean Policy, Office of the Press Secretary, The White House, Mar. 10, 1983.
- Department of State Public Notice 2237, “Exclusive Economic Zone and Maritime Boundaries; Notice of Limits,”(60 Fed. Reg. 43825 (August 23, 1995)).
- Demystifying the Maritime Zones and Other Marine Boundaries on NOAA’S Nautical Charts. Proceedings of the 14th Biennial Coastal Zone Conference, 2005. (paper) and presentation
- Map of the U.S. Exclusive Economic Zone Source: U.S. Commission on Ocean Policy, An Ocean Blueprint for the 21st Century: Final Report (2004) offsite link
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 nautical charts because it continues to be used in certain federal laws. Perhaps the earliest proclamation of the U.S. Three Nautical Mile territorial sea was documented by Secretary of State Thomas Jefferson, Letter to Certain Foreign Ministers of November 8, 1793 (asserting a provisional territorial sea extending a “distance of one sea-league or three geographical miles from the sea shores”) (cannon shot rule). See also U.S. Department of State Geographic Bulletin No. 3 (April 1965) (Longstanding position that the Territorial Sea of the United States and numerous other maritime nations concerned with the Freedom of Navigation is 3 nautical miles citing the Report of the International Law Commission on the Work of its Eighth Session, 23, 4 July 1956, Official Records of the General Assembly, Eleventh Session, Supplement No. 9 (A/3159 offsite link)( The term “mile ” means nautical mile (1,852 metres) reckoned at sixty to one degree of latitude. Page 256).
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 individual U.S. coastal states under the Submerged Lands Act. There are exceptions; therefore, the Three Nautical Mile Line does not necessarily depict the seaward boundaries of all U.S. states in all circumstances 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. Coast Pilot
The continental shelf of a coastal State 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. (The extent of the continental shelf can also be limited by a maritime boundary with another coastal State.)
Where the outer edge of a coastal State’s continental margin extends beyond 200 nm from its baselines, the outer limits of its continental shelf are determined in accordance with Article 76 offsite link of the the Law of the Sea Convention. 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, as well as for other purposes specified in the UN Convention on the Law of the Sea. 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 United States proclaimed jurisdiction and control over its continental shelf in 1945 (Presidential Proclamation No. 2667 of Sept. 28, 1945). Consistent with international law, the United States exercises its continental shelf rights out to a distance of at least 200 nautical miles through several domestic laws. The U.S. Extended Continental Shelf Project, led by the Department of State, NOAA, and the U.S. Geological Survey, determines the outer limits of the U.S. continental shelf beyond 200 nautical miles (i.e., extended continental shelf).
Additional reference information:
- U.S. Department of State, US Extended Continental Shelf (ECS) Project
- NOAA, US Extended Continental Shelf Data
- U.S. Geological Survey, Delineating the US Extended Continental Shelf
- Presidential Proclamation No. 2667, Policy of the United States with Respect to the Natural Resources of the Subsoil and Sea Bed of the Continental Shelf (10 Fed. Reg. 12303 (Sept. 28, 1945)
- White House Press Release, “Proclamations Concerning U.S. Jurisdiction Over Natural Resources of Coastal Areas and High Seas,” 13 Dep’t State Bull. 484 (1945)
- Continental Shelf Convention offsite link (1958)
- Outer Continental Shelf Lands Act, 43 USC § §1331-1356 (defines the Outer Continental Shelf (OCS) as all submerged lands lying seaward of state coastal waters which are under U.S. jurisdiction; states that the jurisdiction asserted by the 1945 Truman Proclamation has the weight of statutory law, 43 U.S.C. 1331, S. REP. No. 133, 83rd Cong. 1st Sess. 2 (1953)
- Department of the Interior, Office of the Solicitor, Authority to Issue Outer Continental Shelf Mineral Leases in the Gorda Ridge Area, M-36952 (May 30, 1985)
United States v. Ray, 294 F. Supp. 532 (SD Fla. 1969) offsite link, aff’d in part, rev’d in part, 423 F.2d 16 (5th Cir. 1970) (construing U.S. authority under the Outer Continental Shelf Lands Act and identifying U.S. rights and interests in the outer continental shelf)
The high seas are comprised of all parts of the sea that are not included in the exclusive economic zone, the territorial sea or the internal waters of a State, or in the archipelagic waters of an archipelagic State.
“Straits used for international navigation” are those that are used or are capable of use for international navigation between one area of the high seas or exclusive economic zone (“EEZ”) and another area of the high seas or EEZ. Part III of the Law of the Sea Convention (articles 34-45 offsite link) describes the regime of transit passage through such straits and the rights, jurisdiction, and duties of the States bordering such straits. Transit passage means the exercise in accordance with Part III of the Law of the Sea Convention of the freedom of navigation and overflight solely for the purpose of continuous and expeditious transit of the strait. LOSC arts. 37, 38 offsite link. The right of transit passage applies throughout straits used or capable of use for international navigation, including to all normally used approaches to and from such straits. Ships and aircraft in transit passage must comply with the duties outlined 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 offsite link. States bordering straits used for international navigation may designate sea lanes and prescribe traffic separation schemes for navigation in accordance with Part III where necessary to promote safe passage of ships. LOSC art. 41 offsite link. They may also adopt laws and regulations relating to transit passage in respect of certain activities, such as fishing. LOSC art. 42 offsite link. 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 offsite link. offsite link
The United States considers itself a strait State (i.e., a State bordering a strait used for international navigation) and in this regard complies with the relevant provisions of international law as reflected in Part III of the Law of the Sea Convention. For example, the United States borders the Bering Strait, which connects the Bering Sea in the Pacific Ocean to the Chukchi Sea in the Arctic Ocean. Although the Bering Strait is 44 nautical miles wide at the narrowest point between the U.S. and Russian mainlands (Cape Prince of Wales, Alaska, and Cape Dezhneva, Siberia), Little Diomede Island (U.S.) and Big Diomede Island (Russia) are located midway between Cape Prince of Wales and Cape Dezhneva. The U.S.-Russia maritime boundary proceeds through the Bering Strait between Little Diomede Island and Big Diomede Island.
Additional Reference Information:
- LOSC Part III offsite link, 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.”)
- Annotated Supplement to the Commander’s Handbook on the Law of Naval Operations, NWP 9 (Rev. A) / FMFM 1-10, Department of the Navy, May 21, 1990 (identifying straits used for international navigation around the world)
- Restatement (Third) of Foreign Relations Law § 513 (1987)
- Richard J. Grunawalt, United States Policy on International Straits, 18 Ocean Dev. & Int’l L. 445 (1987) offsite link
- Lewis M. Alexander, International Straits, 64 Int’l L. Stud. Ser. US Naval War Col. 91 (1991) offsite link
- Arctic Council, Arctic Marine Shipping Assessment (AMSA) 2009 Report offsite link, 106 (“The Bering Strait is a narrow international strait that connects the North Pacific Ocean to the Arctic Ocean and forms the only corridor between northern and east-west transportation routes.”)
- John T. Oliver, U.S. Coast Guard (Ret.), The Right of Transit Passage through the Arctic Straits offsite link, The Coast Guard Journal of Safety & Security at Sea, Proceedings of the Marine Safety & Security Council, Vol. 78, No. 1, 46-51 (Spring 2021)
- Agreement between the United States of America and the Union of Soviet Socialist Republics on the Maritime Boundary, (1 June 1990) TIAS No 11,451 (Senate consideration)
The Area is comprised of the seabed and subsoil beyond the limits of national jurisdiction. It does not include superjacent 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 offsite link, offsite link 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)