How stateless vessels challenge maritime order under UNCLOS?

By Argenis Rodriguez, maritime lawyer

Part 1

The nationality of a ship is one of the most important aspects of maritime law. As is well known, although ships are not people, they must have a nationality to sail; that is, they must be registered in the ship registry of a particular State and fly that State’s flag. It is inconceivable that a ship without a flag or nationality could be put to sea; this would be a flagrant violation of public international law.
Articles 91 and 92 of the United Nations Convention on the Law of the Sea (UNCLOS) establish the requirement that ships have a nationality:

“Article 91
Nationality of ships

Every State shall fix the conditions for the grant of its nationality to ships, for the registration of ships in its territory, and for the right to fly its flag. Ships have the nationality of the State whose flag they are entitled to fly. There must exist a genuine link between the State and the ship.
Every State shall issue to ships to which it has granted the right to fly its flag documents to that effect.”

“Article 92
Status of ships

Ships shall sail under the flag of one State only and, save in exceptional cases expressly provided for in international treaties or in this Convention, shall be subject to its exclusive jurisdiction on the high seas. A ship may not change its flag during a voyage or while in a port of call, save in the case of a real transfer of ownership or change of registry.
“A ship which sails under the flags of two or more States, using them according to convenience, may not claim any of the nationalities in question with respect to any other State, and may be assimilated to a ship without nationality.”

As the Spanish author María Isabel Martínez explains, a ship’s “nationality” serves a different function domestically and internationally. Domestically, nationality acts as a criterion determining the applicability of State laws to private or public relations (between that State and individuals) involving the ship, while internationally it serves to define the powers of States in relation to the ship’s activity, namely, navigation. From this perspective, nationality, in relation to other States, justifies the flag State’s exclusive exercise of its governing authority over the group of people on board, while also identifying it as a potential subject of international obligations pertaining to or affecting that ship¹.

By virtue of their nationality, ships receive the protection of their country’s government, through the respective administrative and military bodies, and correspondingly must follow their orders and submit to the surveillance of warships².

The nationality of a vessel subjects it and its activities to the administrative, criminal, and labor laws of its flag State. It also allows for the application of the principle of exclusive jurisdiction of the flag State on the high seas (territory over which no State has sovereignty). This is derived from Articles 92 and 94 of UNCLOS:

“Article 94
Duties of the flag State

Ships shall sail under the flag of one State only and, save in exceptional cases expressly provided for in international treaties or in this Convention, shall be subject to its exclusive jurisdiction on the high seas. A ship may not change its flag during a voyage or while in a port of call, save in the case of a real transfer of ownership or change of registry” (…).

In summary, ships need to have nationality for the following reasons:

Without it, the ship would not be subject to a single legal system.
Without nationality, on the high seas it would not be subject to any legal system and would not have the protection of any State.
Having nationality means that the flag State exercises continuous control over the ship.

Stateless vessels. Is it possible to assert jurisdiction over them?

In recent years, especially with the proliferation of the so-called “dark fleet” or “shadow fleet”, the presence of stateless vessels has increased significantly, with the aim of carrying out activities considered illicit and evading international sanctions; although not all the vessels that comprise the “dark fleet” are stateless.

Before continuing, what can be understood by “stateless vessels”?

As Ihsan Faruk explains, a vessel is classified as stateless if:

it is not validly registered with any State,
it uses multiple flags for convenience or through fraudulent documentation, or
it flies a flag without legal entitlement.

In such instances, international law deems it legitimate for a warship or a duly authorized government vessel to intervene—specifically, to board the vessel and verify its credentials³. As we have already seen, the flag State has exclusive jurisdiction over its vessels while they are sailing on the high seas. This derives from the sovereignty that the flag State exercises over its vessels and from the right of navigation on the high seas that States have, enshrined in Article 87 of UNCLOS. In principle, no State may board a vessel flagged by another State without first obtaining that State’s permission to do so⁴. However, this guiding principle has a clear exception, represented by the right of visit enshrined in Article 110 of UNCLOS:

“Article 110

Right of visit

Except where acts of interference derive from powers conferred by treaty, a warship
which encounters on the high seas a foreign ship, other than a ship entitled to
complete immunity in accordance with articles 95 and 96, is not justified in boarding
it unless there is reasonable ground for suspecting that:
(a) the ship is engaged in piracy;
(b) the ship is engaged in the slave trade;
(c) the ship is engaged in unauthorized broadcasting and the flag State of the
warship has jurisdiction under article 109;
(d) the ship is without nationality ; or
(e) although flying a foreign flag or refusing to show its flag, the ship is, in
reality, of the same nationality as the warship.
In the cases provided for in paragraph 1, the warship may proceed to verify the
ship’s right to fly its flag. To this end, it may send a boat under the command of an
officer to the suspected ship. If suspicion remains after the documents have been
checked, it may proceed to a further examination on board the ship, which must be
carried out with all possible consideration.
If the suspicions prove to be unfounded, and provided that the ship boarded has not
committed any act justifying them, it shall be compensated for any loss or damage
that may have been sustained.
These provisions apply mutatis mutandis to military aircraft.
These provisions also apply to any other duly authorized ships or aircraft clearly
marked and identifiable as being on government service.” (Emphasis added)

According to this article, a warship of any State may board on the high seas any vessel of a different nationality in cases expressly established in Article 110, as previously cited, including when the vessel being boarded is presumed to have no nationality⁵. Paragraph 2 of Article 110 sets out the steps to be taken if there are well-founded reasons to believe that any of the circumstances described in paragraph 1 of Article 110 are present: first, an officer of the warship will check the vessel’s documentation to determine that it has the right to fly the flag of a sovereign State; after this check, if the officer still suspects any irregularity, they may thoroughly
inspect the vessel, taking all possible consideration toward the vessel, the crew, and the cargo.

Now, the aforementioned article refers to boarding and inspecting the vessel, but it does not expressly establish any power to seize it and subject it to the jurisdiction of the State carrying out the seizure. In cases of piracy and unauthorized transmissions, an express power to arrest the vessel and its crew is established in Articles 105 and 109, respectively. In the specific case of a vessel that has no nationality, no article of UNCLOS establishes an express power to seize the vessel and its crew, nor does it specify what actions to take in this regard, and it is here, in this legal vacuum, that the problems of interpretation begin.

Martínez, María Isabel: Flag and nationality of the ship. ↩︎
De Sola, René: The Nationality of Ships. ↩︎
Ihsan Faruk Kılavuz: Stretching the Law of the Sea: Statelessness and the Seizure of the Skipper. Accessed on January 27, 2026. ↩︎
United Nations Office on Drugs and Crime (UNODC): Maritime crime: a manual for criminal justice practitioners – Third edition, p. 181. Available :
https://www.unodc.org/documents/Maritime_crime/GMCP_Maritime_3rd_edition_Ebook.pdf ↩︎
The State exercising the right of visit will be referred to in this article as the “boarding State”. ↩︎