Freedom of navigation under international law is the right of every nation’s ships to move across the world’s oceans without interference, subject to rules that change depending on how close the vessel is to another country’s coast. The United Nations Convention on the Law of the Sea (UNCLOS), ratified by 170 states and the European Union, sets those rules by dividing the ocean into zones and assigning different rights to coastal states and foreign vessels within each one.1Congress.gov. Implementing Agreements Under the United Nations Convention on the Law of the Sea Roughly 80 percent of global trade moves by ship, and this zonal framework is what keeps it moving.
The convention, opened for signature in 1982 in Montego Bay, Jamaica, is often called the constitution for the oceans.2United Nations. Overview – Convention and Related Agreements It balances two things that pull against each other: a coastal nation’s interest in controlling waters near its shores, and every other nation’s interest in open shipping lanes. The answer to what a ship is allowed to do at any given point depends almost entirely on which zone the ship is in.
The Zones That Decide What a Ship Can Do
Distance from the coast, measured from a baseline that usually follows the low-water line, sets the legal regime. Each zone reduces coastal authority as it moves further out, and expands what foreign vessels can do without asking permission.
Territorial Sea (0 to 12 Nautical Miles)
Within 12 nautical miles of the baseline, a coastal state exercises full sovereignty, much like over its land.2United Nations. Overview – Convention and Related Agreements Foreign vessels still have the right of innocent passage here, but the coastal state regulates safety and pollution and can even suspend passage temporarily in specific areas for security reasons, provided it publishes notice.3United Nations. United Nations Convention on the Law of the Sea
Contiguous Zone (12 to 24 Nautical Miles)
Out to 24 nautical miles, the coastal state does not have sovereignty, but it can enforce its customs, tax, immigration, and sanitary laws to prevent or punish violations that occurred inside its territory.2United Nations. Overview – Convention and Related Agreements It is a buffer for problems that started closer to shore.
Exclusive Economic Zone (Out to 200 Nautical Miles)
The EEZ gives the coastal state sovereign rights over natural resources: fish, oil, gas, and energy from wind and currents, along with jurisdiction over artificial islands, marine scientific research, and environmental protection.4United Nations. United Nations Convention on the Law of the Sea – Part V Exclusive Economic Zone It is not sovereign territory. Every other nation keeps freedom of navigation, freedom of overflight, and the right to lay submarine cables and pipelines.2United Nations. Overview – Convention and Related Agreements A container ship or a warship can transit another country’s EEZ without permission, and the coastal state must show due regard for those rights when exercising its own.
Marine scientific research is the main thing foreign states cannot do in another nation’s EEZ without consent. The coastal state can withhold that consent when the research relates to resource exploration, involves drilling or explosives, or when the researching state has misrepresented the project or has unmet obligations from a previous one.5United Nations. United Nations Convention on the Law of the Sea – Part XIII
Continental Shelf
The continental shelf covers the seabed and subsoil beyond the territorial sea, extending at least 200 nautical miles from the baseline and further if the physical margin does. The outer limit cannot exceed 350 nautical miles from the baseline, or 100 nautical miles from the 2,500-meter depth line, whichever is more favorable.6United Nations. United Nations Convention on the Law of the Sea – Part VI Continental Shelf The coastal state has sovereign rights over the shelf’s natural resources, but those rights do not touch the water column or the airspace above. Ships and aircraft still move freely overhead.
The High Seas
Everything outside national jurisdiction is high seas, and no state can claim any of it. All nations have six freedoms there: navigation, overflight, laying submarine cables and pipelines, constructing artificial islands and installations, fishing, and scientific research.7United Nations. United Nations Convention on the Law of the Sea – Part VII High Seas These freedoms come with a duty to exercise them with due regard for other states. Warships and government non-commercial vessels have complete immunity from any state other than their own flag state while on the high seas.3United Nations. United Nations Convention on the Law of the Sea
Innocent Passage Through the Territorial Sea
Ships of every nation, coastal or landlocked, can pass through any country’s territorial sea under the right of innocent passage. Passage means traveling through without entering internal waters or heading to or from a port, and it must be continuous and expeditious. Stopping is allowed only if it is incidental to ordinary navigation or forced by an emergency such as engine failure or a rescue.3United Nations. United Nations Convention on the Law of the Sea
Passage stops being innocent when the vessel threatens the coastal state’s peace, order, or security. The convention lists what breaks the innocent character of passage: fishing, weapons exercises, launching military devices, serious pollution, surveillance, and any other activity not directly connected to transit.3United Nations. United Nations Convention on the Law of the Sea If a vessel does any of those things, the coastal state can act to prevent the passage.
Coastal nations can also require foreign ships to use designated sea lanes for safety or environmental reasons. Submarines have their own rule: they must travel on the surface and show their flag while transiting the territorial sea.3United Nations. United Nations Convention on the Law of the Sea
Transit Passage Through International Straits
Straits that connect one part of the high seas or an EEZ to another carry a stronger right called transit passage. All ships and aircraft enjoy it, and unlike innocent passage in the territorial sea, transit passage cannot be suspended for any reason. The convention states plainly: “There shall be no suspension of transit passage.”8United Nations. United Nations Convention on the Law of the Sea – Part III Straits Used for International Navigation
The reason is historical. When nations extended their territorial seas from 3 to 12 nautical miles, more than 100 additional straits that had been open water fell inside territorial jurisdiction. The compromise was that these newly enclosed straits would carry a guaranteed right of transit.
The rules of transit passage are more permissive than innocent passage. Submarines may remain submerged. Military aircraft can fly through the airspace over the strait. Vessels have to follow international safety and pollution regulations and stick to activities needed for normal, continuous transit.3United Nations. United Nations Convention on the Law of the Sea The coastal state still governs fishing and navigational aspects but cannot block passage.
This regime covers some of the world’s most strategic waterways. The Strait of Hormuz, only 21 nautical miles wide at its narrowest and handling over 100 major vessel transits per day, sits entirely within the territorial seas of Iran and Oman. Transit passage keeps oil tankers and commercial ships moving through it regardless of political tensions.
Archipelagic Sea Lanes Passage
Nations made up entirely of islands, such as Indonesia and the Philippines, can draw baselines linking their outermost islands and treat the enclosed waters as archipelagic waters. A third passage right applies inside them: archipelagic sea lanes passage. All ships and aircraft can transit through designated lanes and air routes continuously and expeditiously, following all normal international navigation routes. Ships cannot deviate more than 25 nautical miles either side of the lane’s axis and must keep at least 10 percent of the distance between the nearest islands from the coast.9United Nations. United Nations Convention on the Law of the Sea – Part IV Archipelagic States
Outside the designated lanes, ordinary innocent passage applies in archipelagic waters. An archipelagic state can temporarily suspend innocent passage in specific areas for security, but it cannot suspend passage through the designated sea lanes themselves.9United Nations. United Nations Convention on the Law of the Sea – Part IV Archipelagic States
Duties That Come With the Freedom
Freedom of navigation is not freedom from regulation. Ships using any of these passage rights have to comply with international safety and pollution rules set primarily by the International Maritime Organization. The International Convention for the Prevention of Pollution from Ships (MARPOL) governs emissions, waste discharge, and ballast water. The International Convention for the Safety of Life at Sea (SOLAS) sets construction, equipment, and operational standards.10International Maritime Organization. Raft of Shipping Rules in Force From 1 January 2026
New IMO Net-Zero Framework rules are being finalized for adoption in 2026 and expected to enter into force in 2027, requiring ocean-going ships over 5,000 gross tonnage to reduce annual greenhouse gas fuel intensity or acquire offset units.11International Maritime Organization. IMO Approves Net-Zero Regulations for Global Shipping Vessels that violate these standards face detention at port, fines, and the loss of insurance coverage. A coastal state that catches a foreign ship polluting its waters can enforce against it even mid-passage.
Challenging Excessive Claims: Freedom of Navigation Operations
When a country claims maritime authority beyond what UNCLOS allows, other nations push back through Freedom of Navigation Operations (FONOPs). The United States has run its program since 1979 and is the most active operator. The program pairs two things: State Department diplomatic protests and Department of Defense transits sending ships or aircraft through the disputed area to demonstrate that the excessive claim has no legal force.12Department of Defense. Annual Freedom of Navigation Report Fiscal Year 2017
The kinds of claims these operations target include territorial sea claims beyond 12 nautical miles, improper restrictions on innocent passage, requirements that warships get prior permission to transit, baselines drawn to enclose too much sea, and attempts to restrict navigation or overflight in EEZ waters.13USINDOPACOM. Freedom of Navigation Operations
The South China Sea is where this is most active. China, Vietnam, and a handful of other states hold the minority view that UNCLOS lets coastal states regulate foreign military navigation and overflight within their EEZs. The United States and most other countries read the convention as limiting EEZ authority to economic activity, leaving navigation and overflight open. The U.S. Navy routinely operates near the Spratly and Paracel Islands and through the Taiwan Strait, and navies from Japan, Australia, Canada, the United Kingdom, and India have also operated in the South China Sea to reinforce open-access norms.14Congress.gov. China Primer – South China Sea Disputes These operations are peaceful. The point is to create a legal record of objection so an excessive claim does not harden into accepted practice.
Resolving Disputes and Freeing Detained Ships
UNCLOS created the International Tribunal for the Law of the Sea to hear disputes over the convention’s interpretation and application.15International Tribunal for the Law of the Sea. The Tribunal Its most navigation-relevant function is prompt release. When a coastal state seizes a foreign vessel and refuses to release it after a reasonable bond is posted, the flag state can file an application under Article 292. The tribunal gives these applications priority, holds a hearing within 15 days, and issues judgment within 14 days of the hearing’s close. If the detention is unjustified, the tribunal sets the bond required for release.16International Tribunal for the Law of the Sea. Prompt Release of Vessels and Crews
States can also opt out of binding dispute resolution for certain categories, including military activities. The most politically charged confrontations at sea therefore often fall outside the tribunal’s reach and get handled through diplomacy.
Where the United States Fits
The United States has not ratified UNCLOS and is the most prominent non-party. It signed the convention in 1994, but the Senate has never consented to ratification. The main objection has been Part XI, which governs deep seabed mining and raises economic and sovereignty concerns.
Even so, the United States treats most of the convention as binding customary international law. Presidential Proclamation 5030 in 1983 claimed a 200-nautical-mile EEZ, and Presidential Proclamation 5928 in 1988 claimed a 12-nautical-mile territorial sea, both matching UNCLOS.17Congress.gov. United Nations Convention on the Law of the Sea (UNCLOS) U.S. freedom of navigation operations are conducted under the same rules the convention lays down, and American courts and policymakers cite UNCLOS as reflecting the accepted legal order at sea.