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United Nations Convention on the Law of the Sea (UNCLOS)

United Nations Convention on the Law of the Sea (UNCLOS)


Technological advancements during the last century led nations to compete for and exploit the ocean and its resources at an unprecedented level. Large fishing vessels that could remain at sea for months at a time depleted fish stocks. The discovery of oil, gas, and minerals under the seabed led to a competition to claim areas of the sea that held this wealth. The magnitude of these activities also had a profound effect on the environment as dwindling fish populations and increased pollution destroyed coastal ecosystems.

Over 160 nations met in the Third United Nations Conference on the Law of the Sea to address the issues surrounding use of the oceans. After nine years of negotiations, the conference adopted the United Nations Convention on the Law of the Sea (UNCLOS). UNC-LOS addressed the territorial limits of nations over the ocean, economic rights to the ocean’s resources, and rights of transit. UNCLOS also addressed pollution and other environmental concerns. Article 192 of UNCLOS states that all nations have a general obligation “to protect and preserve the environment.” Even though UNC-LOS was not strictly intended to be an environmental treaty, it has had a profound effect on environmental regulation in the oceans.

Historical Background and Scientific Foundations

Until the mid-twentieth century, most nations adhered to the freedom-of-the-seas doctrine, which originated in the seventeenth century. The freedom-of-the-seas doctrine granted nations jurisdiction over the oceans for an area extending three nautical mi (5.5 km) from shore. Nations considered the waters beyond this three-mile limit to be international waters that were open to all nations but not belonging to any one nation in particular.

By the mid-twentieth century, deep-sea discoveries and technological advancements led several nations to question the continued utility of the freedom-of-the-seas doctrine. In the early twentieth century, valuable metals and diamonds were discovered in the oceans, which raised the possibility of unrestricted deep-sea mining. Offshore petroleum and gas reserves were also discovered on continental shelves in the North Sea and off the coast of North America. The first offshore oil drilling occurred in the Gulf of Mexico in 1947. By the late 1960s, oil production in the Gulf of Mexico had grown to nearly 400 million tons of oil per year.

In 1945, in order to protect oil, gas, and mineral reserves, U.S. President Harry Truman declared that the United States had jurisdiction over the entire continental shelf. President Truman’s declaration made the United States the first nation to abandon the freedom-of-the-seas doctrine.

Other nations followed suit and abandoned the freedom-of-the-seas doctrine in order to protect mineral deposits, petroleum reserves, and rapidly depleting fish stocks. Many nations also became concerned about the environmental damage caused by pollution and overfishing. Nations soon became involved in numerous territorial and sovereignty claims as they competed for the oceans’ vast resources and debated the issue of the rights of ships to pass through their waters.

In 1967, Arvid Pardo, Malta’s ambassador to the United Nations, called on all nations to address the environmental, economic, legal, and political issues surrounding the exploration and use of the oceans and seabed. In 1973, the Third United Nations Conference on the Law of the Sea convened in New York City. Nine years later, in 1982, the conference adopted the United Nations Convention on the Law of the Sea (UNCLOS).


CONTIGUOUS ZONE: A maritime zone extending 24 nautical miles (44 km) from the outer edge of the territorial sea, in which a coastal state can exert limited control of its laws.

CONTINENTAL SHELF: A gently sloping, submerged ledge of a continent.

DEEP SEA MINING: The extraction of valuable mineral deposits from the ocean floor; not yet practiced due to legal, environmental, and monetary concerns.

EXCLUSIVE ECONOMIC ZONE (EEZ): A maritime zone extending 200 nautical miles (370 km) from the outer edge of the territorial sea, in which a coastal state has special rights over the exploration and use of marine resources.

FREEDOM-OF-THE-SEAS DOCTRINE: An eighteenth-century agreement establishing the right of neutral shipping in international waters.

INNOCENT PASSAGE: The right of all ships to pass through the territorial waters of another state subject to certain restrictions.

TERRITORIAL WATER: A maritime zone of coastal waters extending up to 12 nautical miles (22 km) from the baseline of a coastal state, within which a state can exert control of its laws and regulations.

TRANSIT PASSAGE: The right of free navigation and over-flight for the purpose of continuous transit through a strait between one part of the high seas and another.

UNCLOS replaced the three-nautical-mile limit that existed under the freedom-of-the-seas doctrine with a tiered approach. UNCLOS expanded each nation’s territorial waters to 12 nautical mi (22 km). Within territorial waters, a nation can set and enforce laws, regulate use, and exploit resources. UNCLOS also allowed for an additional 12-mile contiguous zone where a nation could enforce smuggling and immigration laws. Under UNCLOS, ships from one nation may pass through the territorial waters of another nation under the right of innocent passage. Under the right of transit passage, military vessels may pass through the territorial waters of another country when other opportunities do not exist, such as passing through a strait.

The establishment of exclusive economic zones (EEZs) was one of the most important features of UNCLOS. Under UNCLOS, each nation has the exclusive right to use, exploit, or develop any resource that lies within 200 nautical mi (370 km) of its coastline. This placed 38 million square nautical miles of ocean and seabed under the exclusive control of individual countries. Virtually all fish stocks, most deep-sea minerals, and nearly 87% of all offshore oil and gas reserves now lie within a specific EEZ.

Although EEZs carry an obvious economic benefit, the establishment of EEZs has also had an impact on environmental regulation. Under UNCLOS, a nation has the ability to conserve the natural resources that lie within its EEZ. Nations can now prevent foreign nations from depleting fish stocks, extracting minerals, and drilling for oil within its EEZ. The drafters of UNCLOS envisioned that a nation would be more likely to take precautions to prevent environmental accidents when the consequences of a disaster would affect its own coastal ecosystem.

Impacts and Issues

Although UNCLOS is not expressly an environmental treaty, the scope and relatively universal acceptance of UNCLOS make it one of the most influential treaties regarding the environment. Part XIII of UNCLOS addresses the protection and preservation of the marine environment, including the following sources of pollution: land-based pollution, deep-sea mining, dumping, vessel-source pollution, continental shelf drilling, and pollution from or through the atmosphere. UNCLOS permits states to enforce their anti-pollution and other environmental standards throughout their EEZs, except those concerning vessel-source pollution.

Each nation has the right to exploit all mineral resources that lie within its EEZ. Although most minerals are located within the EEZ of a particular nation, Part XI of UNCLOS addresses mineral resources that lie in international waters. Currently, the technology does not exist to remove minerals located at such great depths. Part XI established the International Seabed Authority (ISA) to regulate mining in international waters. The United States objected to the establishment of the ISA. As a result, the U.S. Senate has not ratified UNCLOS. The United States is a signatory to UNCLOS, however, and regards all of its remaining provisions as binding customary international law.

Finally, global climate change has greatly increased the importance of the UNCLOS provisions regarding the right of foreign ships to pass through another nation’s waters. As noted, UNCLOS states that a nation’s vessels may pass through the territorial waters of another nation under the right of innocent passage. In 2007, the loss of Arctic sea ice due to global climate change led to the opening of the Northwest Passage for the first time in recorded history. The Northwest Passage provides a shortcut from the North Atlantic to the Pacific Ocean by passing through a chain of Canadian islands known as the Canadian Arctic Archipelago. Scientists predict that the Northwest Passage will open regularly during summer months because of global climate change.

A dispute over international waters erupted over transit through the Northwest Passage. Most nations, including the United States and most European nations, regard the Northwest Passage as a strait through which foreign vessels have the rights of innocent passage and transit passage of military vessels. Canada claims that the Northwest Passage is part of its internal waters and not part of its territorial waters. A nation may prohibit all use of its internal waters, including the right of innocent passage. A similar international dispute is likely to occur when the Northeast Passage, a passage through the Russian Arctic, is ice-free in the near future.

See Also Coastal Ecosystems; Oceans and Coastlines; Overfishing; Water Conservation; Water Pollution; Water Resources



Churchill, R. R., and A. V. Lower. The Law of the Sea. Huntington, NY: Juris, 1999.


Halfar, Jochen, and Rodney M. Fujita. “Danger of Deep-Sea Mining: Plans for Deep-Sea Mining Could Pose a Serious Threat to Marine Ecosystems.” Science 316 (2007): 987.

Web Sites

Canadian Broadcasting Corporation. “Arctic Sovereignty: Drawing a Line in the Water.” August 2, 2007. (accessed January 31, 2008).

National Geographic. “Arctic Melt Opens Northwest Passage.” September 17, 2007. (accessed January 31, 2008)

United Nations. “United Nations Convention on the Law of the Sea.” (accessed January 31, 2008)

United Nations. “The United Nations Convention on the Law of the Sea: A Historical Perspective.” (accessed January 31, 2008).

U.S. Department of State. “The UN Convention on the Law of the Sea: Written Testimony Before the Senate Foreign Relations Committee of John D. Negroponte, Deputy Secretary of State.”September 27, 2007. (accessed January 31, 2008).

Joseph P. Hyder
Adrienne Wilmoth Lerner

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