Freedom of Navigation Operations are transits by U.S. military ships and aircraft through waters or airspace where a foreign government has imposed a restriction that the United States considers unlawful under international law. The point is to demonstrate, by doing, that the restriction has no legal force. The operations run alongside formal diplomatic protests filed by the State Department, and together they make up the Freedom of Navigation program that has operated continuously since 1979. In Fiscal Year 2023, U.S. forces challenged 29 excessive maritime claims advanced by 17 different countries.1U.S. Indo-Pacific Command. DOD Releases Fiscal Year 2023 Freedom of Navigation Report
Why the United States Runs the Program
The legal position behind FONOPs is a little unusual. The United States has never ratified the UN Convention on the Law of the Sea, the main treaty governing ocean use. Every administration since the treaty was adopted has nevertheless treated its navigation and overflight provisions as customary international law — longstanding practices that bind all nations whether or not they signed the treaty.2Defense Technical Information Center. A Constitution for the Oceans – How Would U.S. Ratification of the United Nations Convention on the Law of the Sea (UNCLOS) Affect U.S. National Interests That gives the government a framework for contesting foreign restrictions without being a party to the convention.
The Carter administration created the program in 1979 after concluding that diplomatic protests on their own were not enough to counter the growing number of expansive maritime claims worldwide. Ships actually sailing through disputed waters carried weight that written objections did not.3U.S. Naval War College. U.S. Freedom of Navigation Program That reasoning still defines how the program works today.
What Counts as an Excessive Claim
The Freedom of Navigation program targets what it calls “excessive maritime claims” — restrictions on navigation or overflight that international law does not permit. A single operation is planned against a specific claim, and the categories tend to repeat.
One is improper straight baselines. A nation may connect headlands with straight lines only where its coastline is deeply indented or fringed by islands. Some countries draw those lines far more aggressively than the geography justifies, and every downstream maritime zone — territorial sea, contiguous zone, EEZ — pushes further out with them. China’s baselines in the South China Sea are a prominent example.
Another is prior-notification or consent requirements for warships entering a territorial sea. The United States treats these as a direct violation of the right of innocent passage, which applies to all ships without administrative preconditions.4United Nations. United Nations Convention on the Law of the Sea – Part II A typical FONOP against this kind of claim involves a Navy destroyer sailing through the territorial sea without giving any advance notice.
Some coastal states declare security zones extending well beyond the 12-nautical-mile territorial sea, attempting to restrict foreign military activity in what is legally international water. Others try to apply Air Defense Identification Zone rules to aircraft that are merely passing through, rather than entering national airspace.5U.S. Naval War College Digital Commons. International Law Studies – Air Defense Identification Zones
And at least 17 nations, including China, India, Brazil, and Indonesia, have tried to restrict foreign military activities inside their exclusive economic zones — banning intelligence collection, surveys, or exercises, or requiring consent for them.6U.S. Naval War College. Military Activities in the Exclusive Economic Zone The U.S. position is that UNCLOS reserves coastal-state authority over military activities to the territorial sea and archipelagic waters only, and that freedoms of navigation and overflight extend into any nation’s EEZ.7United Nations. United Nations Convention on the Law of the Sea – Part V
How an Operation Actually Unfolds
The Department of Defense runs the operational side of the program using assets from the Navy, Air Force, and Coast Guard.8U.S. Department of Defense. Freedom of Navigation Program Fact Sheet What the Pentagon calls an “operational assertion” happens when a military vessel or aircraft deliberately enters an area subject to an excessive claim and conducts its transit as if the restriction does not exist. If a country requires prior notification for warships in its territorial sea, a Navy destroyer transits without notifying anyone. If a country claims jurisdiction over military flights in its EEZ, an Air Force aircraft flies the route without seeking permission.
Every operation is planned against a specific claim, reviewed by lawyers, and approved through the chain of command. The vessel or aircraft does exactly what international law permits and nothing more. The program also counts secondary assertions: operations with a different primary mission that happen to transit a disputed area, effectively challenging the claim as a byproduct.8U.S. Department of Defense. Freedom of Navigation Program Fact Sheet
The physical operation is only half of it. The State Department files formal diplomatic notes with the foreign ministries of nations making excessive claims, protesting the legal basis of the restriction.9U.S. Department of State (archived). Digest of United States Practice in International Law 2013 A physical assertion without a legal explanation could be dismissed as a provocation. A written protest without physical follow-through could be dismissed as empty rhetoric. Consistent, documented objection also matters for customary international law — it prevents excessive claims from ripening into accepted practice over time.
Each year the Pentagon publishes an unclassified report listing which nations were challenged and which claims were at issue, making the program one of the more transparent elements of U.S. military operations.8U.S. Department of Defense. Freedom of Navigation Program Fact Sheet
Why Warships Can Do This
The program relies on military assets rather than commercial vessels because of sovereign immunity. Under international law, warships on the high seas are completely immune from the jurisdiction of any nation other than their flag state.10United Nations. United Nations Convention on the Law of the Sea – Part VII No foreign coast guard can board, inspect, or detain a warship conducting a FONOP. Government ships used for non-commercial purposes get the same protection. Even inside a foreign territorial sea, UNCLOS preserves warship immunities — the coastal state’s remedy for a warship that ignores its rules is to require it to leave, not to seize it.11United Nations. United Nations Convention on the Law of the Sea A commercial vessel transiting the same waters could face boarding, detention, or fines. A warship cannot.
Safety Protocols in Play
FONOPs are designed to be legally assertive without being militarily dangerous. Two frameworks govern how military vessels and aircraft behave when they meet at sea. The 1972 Agreement on the Prevention of Incidents On and Over the High Seas, originally with the Soviet Union and now with Russia, sets baseline rules: follow international collision regulations, stay clear of other ships, do not simulate attacks, do not aim weapons or shine searchlights at bridges, do not perform aerobatics over the other side’s ships.12U.S. Department of State. Agreement Between the Government of the United States of America and the Government of the Union of Soviet Socialist Republics on the Prevention of Incidents On and Over the High Seas The 2014 Code for Unplanned Encounters at Sea, adopted by the Western Pacific Naval Symposium, is voluntary but sets standardized communication procedures for a wider group of navies, including radio contact in English on VHF Channel 16 and prohibitions on simulated attacks or use of fire-control radars.13Western Pacific Naval Symposium. Code for Unplanned Encounters at Sea (CUES)
These protocols don’t prevent all friction. Chinese warships routinely shadow and challenge U.S. vessels during South China Sea FONOPs, and close encounters have produced real collision risks. But the agreed standards give both sides a framework for de-escalation.
What Happens If Someone Shoots
No FONOP has escalated to an exchange of fire. If one ever did, the UN Charter’s Article 51 preserves the inherent right of self-defense in the event of an armed attack, lasting until the Security Council acts, and any measures taken must be immediately reported to the Council.14United Nations. Repertory of Practice of United Nations Organs – Article 51 The program’s value depends on staying below that threshold. A FONOP that triggers a military confrontation has failed at its purpose of demonstrating the normalcy and legality of transit.
Where FONOPs Happen and Against Whom
The program is applied globally and non-discriminatorily. The United States uses identical legal standards against allies, partners, and adversaries.3U.S. Naval War College. U.S. Freedom of Navigation Program That is a deliberate choice. If the United States only challenged Chinese claims, the program would look like a political instrument. By treating every excessive claim as equally worth contesting, the government keeps the exercise anchored in law rather than rivalry.
The South China Sea draws the most public attention because multiple nations maintain overlapping expansive claims there and China’s response tends to generate headlines. In August 2025, the destroyer USS Higgins transited near Scarborough Shoal while two Chinese frigates shadowed the operation. That kind of encounter is routine: noticeable, carefully managed, and resolved without incident.
The Persian Gulf and Mediterranean see consistent activity because of the international straits that run through them. The Strait of Hormuz and the Turkish Straits are essential corridors for global energy and commerce, so any attempt to restrict transit through them becomes a priority for the program. Operations also cover the Caribbean, Indian Ocean, Arctic, and waters around Pacific island chains. The geographic breadth is part of the message: these navigation rights belong to everyone, and the program is meant to keep it that way.