The law of the sea is the body of international rules that governs how countries use the ocean. It defines coastal zones and assigns rights over resources while protecting navigation. Its frameworks cover marine research and environmental protection, along with procedures for disputes between states.
NOAA’s account of the law of the sea traces the modern system through twentieth-century conferences and the 1982 United Nations Convention on the Law of the Sea. The convention entered into force in 1994 and is often called UNCLOS.
The rules begin at a coastal baseline and extend outward through several legal zones. A country has different authority in each zone. Distance alone does not settle every question because neighboring coasts, islands and the shape of the continental margin can complicate boundaries.
UNCLOS provides the central framework
Customary law governed ocean activity long before a single global convention existed. By the twentieth century, offshore technology joined expanding shipping in creating pressure for clearer limits. Countries also needed shared rules governing fisheries and seabed resources while protecting passage through narrow straits.
The United Nations held its first law-of-the-sea conference in 1956. Four conventions emerged in 1958. Their subjects included the territorial sea and continental shelf. Negotiations continued because important questions, especially the width of coastal zones, remained unsettled.
The third conference produced UNCLOS in Montego Bay in 1982. Its provisions address navigation and resource rights, with a further framework for protecting the marine environment. The text also established institutions for the international seabed and created ways to resolve certain disputes.
The United Nations convention index shows the breadth of the agreement, from baselines and innocent passage to scientific research. Specific articles matter because broad labels such as territorial sea carry defined legal consequences.
Baselines anchor maritime zones
Most maritime distances are measured from a baseline along the coast. Under the usual rule, the normal baseline follows the low-water line shown on officially recognized large-scale charts. Special geography may justify straight baselines connecting selected coastal points.
Baselines can move when the legally relevant shoreline changes through erosion or accretion. NOAA describes ordinary U.S. baselines as ambulatory. The agency maps them using chart information and coordinates with other federal bodies when maritime limits are updated.
Islands can generate maritime zones when they meet the convention’s legal criteria. Rocks that cannot sustain human habitation or an economic life of their own receive narrower treatment for the exclusive economic zone and continental shelf. Disagreement over a small feature can therefore affect a large area of ocean.
Opposite or adjacent coasts may create overlapping claims. States can negotiate a boundary or submit a dispute to an agreed process. They may establish provisional arrangements while the issue remains unresolved. A 200-nautical-mile entitlement never guarantees an uncontested 200-mile zone in every direction.
Charts and lists of geographic coordinates make legal limits usable at sea. Survey quality influences the technical work behind those lines, as do datums and shoreline change.
The territorial sea extends up to 12 miles
A coastal state may establish a territorial sea reaching no more than 12 nautical miles from its baselines. Sovereignty extends through the water column to the seabed, subsoil and airspace above it, subject to international law.
Foreign ships retain a right of innocent passage. Passage must be continuous and expeditious, although stopping can be allowed for ordinary navigation or distress. Activities that threaten the coastal state or fall outside the convention’s definition can make passage non-innocent.
The official UNCLOS territorial-sea text sets the 12-mile limit and describes coastal-state authority. It also covers bays and straits, including geographic cases that cannot be reduced to one circle drawn from shore.
The contiguous zone reaches 24 miles
Beyond the territorial sea, a state may claim a contiguous zone extending no farther than 24 nautical miles from the baseline. Authority there is narrower than sovereignty in territorial waters.
The coastal state may act to prevent or punish violations of customs, fiscal, immigration or sanitary laws connected with its territory or territorial sea. The zone supports enforcement before a vessel reaches shore or after it leaves.
Navigation freedoms continue in this area. A contiguous zone should therefore be understood by its specific enforcement powers instead of as a second territorial sea.
The EEZ can reach 200 miles
The exclusive economic zone, or EEZ, may extend up to 200 nautical miles from the baseline. A coastal state has sovereign rights over natural resources in the water and seabed. Those rights include exploration as well as conservation and management.
Those rights include fisheries and energy production. The coastal state also has defined jurisdiction over artificial islands, marine scientific research and environmental protection. Other states retain freedoms of navigation and overflight, along with the laying of submarine cables and pipelines.
Part V of UNCLOS defines the legal regime of the EEZ. The balance separates resource authority from full sovereignty, allowing international movement through an economically controlled zone.
Countries must conserve living resources and consider the effects of exploitation. Migrating fish stocks frequently cross borders or move onto the high seas, so effective management may require regional agreements.
Continental shelf rights concern the seabed
The legal continental shelf consists of seabed and subsoil, not the water above. Coastal states possess rights over its mineral and other nonliving resources, plus organisms legally classed as sedentary species.
Every coastal state has shelf rights to at least 200 nautical miles where geography permits. If the continental margin continues farther, UNCLOS supplies technical formulas subject to outer constraints for an extended shelf. Supporting a claim requires geologic evidence supported by bathymetric measurements.
Water-column rights above an extended shelf may belong to the high-seas regime or another state’s EEZ. The distinction explains why one location can be governed by different rules at different depths.
The U.S. Department of State’s extended continental shelf overview explains the legal shelf as an extension of land territory beneath the sea. Its archived status does not change the geographic evidence used in the completed U.S. delineation.
Beyond national shelves lies “the Area,” whose mineral resources UNCLOS treats as the common heritage of humankind. The International Seabed Authority organizes and controls related activities for states that are parties to the convention.
The high seas preserve shared freedoms
Waters beyond national EEZs remain the high seas. Ships enjoy navigation under the jurisdiction of their flag state, while all states have recognized freedoms for activities allowed by international law.
Freedom does not mean absence of rules. Treaties address piracy alongside marine pollution and conservation. Flag states carry duties concerning vessels registered under their authority and specialized agreements manage particular fisheries or environmental risks.
UNCLOS also protects transit through straits used for international navigation. Transit passage provides broader movement than innocent passage in many strategically important waterways, while ships and aircraft must proceed without delay and respect applicable safety rules.
The U.S. position has two layers
The United States ratified the 1958 conventions but has not joined UNCLOS as a party. It nevertheless recognizes many convention provisions as customary international law and follows them in its ocean policy.
That position distinguishes treaty membership from acceptance of rules that have become customary through widespread state practice and legal conviction. The difference affects participation in convention institutions even when daily navigation rules are broadly observed.
A State Department explanation of the U.S. approach to UNCLOS describes its acceptance of the convention’s balance for traditional ocean uses. Debate over formal accession has continued through multiple administrations and Congresses.
NOAA’s practical role includes mapping the 12-mile territorial sea, 24-mile contiguous zone and 200-mile EEZ on nautical charts. These boundaries influence enforcement and resource management. They also affect government planning, which is why chart updates involve legal review as well as surveying.
The law of the sea converts an open, connected ocean into a structured legal space. Its zones do not resemble fences on the water. They allocate particular rights and duties while preserving the navigation that connects countries across the globe.
Related reading: the historical meaning of the Seven Seas and the location of Point Nemo.
