This article focuses on the application of the broad principles of freedom of the high seas and navigation rights, as outlined in the LOSC, within specific situations that permit coastal States to impose some limitations on freedom of navigation including “innocent passage” and “transit passage.”  The U.S. is not a party to the LOSC, but it considers the provisions of the Convention relating to the high seas and navigation rights to be a reflection of the customary international law that is binding on all States.

This article analyzes the legal definition of innocent passage by vessels through territorial waters and discusses the relevant articles of the LOSC regarding innocent passage. It then outlines the legal definition of transit passage through international straits and discusses the relevant articles of the LOSC regarding transit passage. The right of archipelagic sea lanes passage for ships and aircraft is also part of the freedom of navigation framework within the LOSC, but it will not be addressed in depth here. The final section highlights the U.S. Freedom of Navigation Program, which is designed to challenge unlawful limitations imposed by coastal States in some of the most hotly contested waters around the globe.

Right of Innocent Passage

The right of innocent passage for foreign vessels within the territorial sea of a coastal State is defined as “navigation through the territorial sea for the purpose of (a) traversing that sea without entering internal waters or calling at a roadstead or port facility outside internal waters; or (b) proceeding to or from internal waters or a call at such roadstead or port facility.” Passage must be “continuous and expeditious,” but it may include stopping and anchoring when incidental to ordinary navigation or rendered necessary by unusual circumstances.

Article 19 of the LOSC declares that passage is “innocent” so long as it is not prejudicial to the peace, good order, or security of the coastal State and further outlines a list of 12 activities that are considered “prejudicial.” This list effectively precludes a range of military operations, including practicing or exercising weapons; collecting information to the prejudice of the coastal State; launching, landing or taking on board any aircraft or military device; and jamming coastal State communications. Submarines and underwater vehicles conducting innocent passage must navigate on the surface and show their flag. It is important to note that the right of innocent passage only applies to foreign vessels. Aircraft in flight are not entitled to innocent passage and thus aircraft must remain onboard vessels during innocent passage.

An exception to the authority to deny innocent passage to aircraft exists within the limited context of the “right of assistance entry” based on the long-recognized duty of mariners to render immediate rescue assistance to those in danger or distress at sea. The right of assistance entry permits entry into the territorial sea by ships or, under certain circumstances, aircraft without permission of the coastal State for the limited purposes of rescue or assistance. This principle of customary international law is also reflected in the “duty to render assistance” described in Article 98 of the LOSC.

The right of innocent passage applies to straits used for international navigation in accordance with the LOSC and cannot be suspended even when a situation of armed conflict exists. The right of innocent passage also applies to archipelagic waters, but it can be subject to temporary published suspensions for the protection of coastal State security.

Laws and Regulations of the Coastal State Relating to Innocent Passage

Article 24 prohibits coastal States from hampering the innocent passage of foreign ships through the territorial sea unless specifically authorized by other Articles of the LOSC. Coastal States are also prohibited from discriminating among States or cargoes from different nations. However, the LOSC permit coastal States to adopt laws
and regulations related to passage through the territorial sea in the following list of circumstances:

  • The safety of navigation and the regulation of maritime traffic;
  • The protection of navigational aids and facilities and other facilities or installations
  • The protection of cables and pipelines;
  • The conservation of the living resources of the sea;
  • The prevention of infringement of the fisheries laws and regulations of the coastal State;
  • The preservation of the environment of the coastal State and the prevention, reduction and control of pollution thereof;
  • Marine scientific research and hydrographic surveys;
  • The prevention of infringement of the customs, fiscal, immigration or sanitary laws and regulations of the coastal State;
  • Prevention of collisions at sea including the use of designated sea lanes and traffic separation schemes; and
  • Require foreign nuclear-powered ships and ships carrying nuclear or other inherently dangerous or noxious substances to carry documents and observe special precautionary measures established for such ships by international agreements.

Despite the broad regulatory authority outlined above, Article 26 of the LOSC prohibits the imposition of charges levied upon foreign ships for innocent passage unless a ship receives services rendered by the coastal State for which payment is due, such as refueling or maintenance.

Rights of Protection of the Coastal State

A coastal State may take necessary steps in its territorial sea to prevent passage which is not innocent and may announce temporary suspensions of innocent passage through a required public notice if the suspension is essential for security reasons, which include weapons exercises. While the text of the relevant articles of the LOSC does not explicitly grant the right of innocent passage to warships, the overall language of the LOSC in the context of its negotiation history and customary international law all make it clear that warships enjoy the right of innocent passage on an unimpeded and unannounced basis. 

However, if a warship does not comply with coastal State regulations that conform to established principles of international law and disregards a request for compliance that is made to it, the coastal State may require the warship to leave the territorial sea immediately. Due to the sovereign immunity of warships (discussed further in Chapter Six: Sovereign Immunity) the degree to which a coastal State can force a warship to exit its territorial waters in this situation is not clear. Additionally, coastal States may not prohibit transit or otherwise impair the rights of innocent passage of nuclear-powered sovereign vessels.

Differing Interpretations Regarding Innocent Passage

Several articles of the LOSC addressing innocent passage have led to differing interpretations by States. For example, some coastal States interpret Article 19(1), which allows for innocent passage, to prohibit several activities not explicitly listed under Article 19(2). Another issue of interpretation is whether the coastal State may require foreign ships conducting innocent passage to carry equipment that enables the coastal State to monitor the ship’s movement. Some commentators have argued that no LOSC provision prevents the coastal State from imposing such a measure. However, the LOSC does not expressly characterize a foreign ship’s passage in the territorial sea as non-innocent if it fails to enable monitoring by the coastal State.

These disputed issues originate from the negotiations that preceded the adoption of the LOSC, which placed the interests of maritime powers in conflict with those of coastal States. Maritime powers pushed for more freedom of navigation, but coastal States argued for the ability to constrain mobility in certain circumstances to protect coastal State interests.

Unlawful Restrictions Claimed by Outlier States

A number of States unlawfully require prior notification before a foreign warship may conduct innocent passage through their territorial waters, but most of these States do not specify when the foreign warship must provide the notification. A larger number of States, notably including China, not only unlawfully require notification, but also require that prior permission be granted.

Saudi Arabia unlawfully asserts that innocent passage does not apply to its territorial sea where there is an alternate route through the high seas or an exclusive economic zone (EEZ) which is equally suitable.

Romania and Lithuania prohibit the passage of ships carrying nuclear and other weapons of mass destruction through their territorial seas.

Right of Transit Passage

The right of transit passage is defined as the exercise of the freedoms of navigation and overflight, solely for the purpose of continuous and expeditious transit through an international strait between one part of the high seas or an EEZ and another part of the high seas or an EEZ, in the normal modes of operation utilized by ships and aircraft for such passage. An exception to the right of transit passage declares that the right “shall not apply if the strait is formed by an island of a State bordering the strait and its mainland” and “there exists seaward of the island a route through the high seas or through an exclusive economic zone of similar convenience with respect to navigational and hydrographical characteristics.”

Transit passage cannot be hampered or suspended by the coastal State for any purpose during peacetime. This also applies to transiting ships, including warships, of States at peace with the bordering coastal State but involved in armed conflict with another State. The right of transit passage applicable in peacetime, along with the laws and regulations of States bordering straits adopted in accordance with international law, continue to apply during armed conflict. However, during transit belligerents must not conduct offensive operations against enemy forces, nor use such neutral waters as a place of sanctuary or as a base of operations.

It is important to note a few key differences between innocent passage and transit passage that are particularly relevant to military operations and to highlight the fact that fewer restrictions may be imposed on transit passage when compared to innocent passage. While there is no right to innocent passage for aircraft, and coastal States may deny entry to aircraft attempting to traverse airspace over their territorial waters, they may not deny transit passage to aircraft over an international strait.

In addition, while coastal States may require submarines to conduct innocent passage on the surface and showing their flag, they may not prohibit submarines from conducting transit passage submerged. Another difference is that transit passage may not be suspended by the coastal State, whereas innocent passage may be temporarily suspended.

Duties of Ships and Aircraft During Transit Passage

Ships and aircraft exercising the right of transit passage shall (a) proceed without delay through or over the strait; (b) refrain from any threat or use of force against the sovereignty, territorial integrity, or political independence of States bordering  the strait; and (c) refrain from any activities other than those incident to their normal modes of continuous and expeditious transit unless rendered necessary by force majeure or by distress. Surface warships may transit in a manner consistent with sound navigational practices and the security of the force, including the use of their electronic detection and navigational devices such as radar, sonar, and depth sounding devices, formation steaming, and the launching and recovery of aircraft.

Laws, Regulations, & Duties of States Bordering Straits Relating to Transit Passage

Foreign ships are required to obtain the authorization of the coastal States that border straits prior to carrying out any research or survey activities while exercising the right of transit passage. States bordering straits have the authority to establish sea lanes and traffic separation schemes where necessary to promote the safe passage of ships in straits used for international navigation. Warships, auxiliaries, and government ships operated on exclusive government service, i.e., sovereign-immune vessels, are not legally required to comply with such sea lanes and traffic separation schemes while in transit passage, but they must exercise due regard for the safety of navigation. Coastal States may not prohibit transit or otherwise impair the right of transit passage of nuclear-powered sovereign vessels.

Coastal States have the authority to adopt laws and regulations relating to transit passage through straits, with respect to all or any of the following:

(a) The safety of navigation and the regulation of maritime traffic, as provided in Article 41;

(b) The prevention, reduction and control of pollution, by giving effect to applicable international regulations regarding the discharge of oil, oily wastes and other noxious substances in the strait;

(c) With respect to fishing vessels, the prevention of fishing, including the stowage of fishing gear;

(d) The loading or unloading of any commodity, currency or person in contravention of the customs, fiscal, immigration or sanitary laws and regulations of States bordering straits.

States bordering straits have the duty not to hamper transit passage and to give appropriate publicity to any danger to navigation or overflight within or over the strait of which they have knowledge.


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