Maritime boardingsand international law:The Venezuela context
- Jennifer Parker
- 10 hours ago
- 4 min read
9 January 2025 | Jennifer Parker
Image: US European Command Twitter
Recent US boardings of oil tankers linked to Venezuela have prompted claims of piracy and illegality under international law. In reality, many of these boardings rest on a sound legal basis. Boarding vessels at sea is a routine naval activity permitted in limited circumstances under international law. This explainer outlines the international law governing maritime boardings and how it applies to the Venezuela cases.
Boarding operations on the high seas, beyond the 200-nautical-mile exclusive economic zone, are governed by the UN Convention on the Law of the Sea (UNCLOS). While the US has not ratified UNCLOS because of domestic concerns over its deep seabed provisions, it recognises the Convention as reflecting customary international law and complies with it.
Under UNCLOS, any warship may board a vessel on the high seas if it is stateless.
Recent commentary has described US boardings as piracy, a term often used loosely. In law, piracy has a narrow definition under UNCLOS; it is limited to violent acts carried out for private ends by private vessels on the high seas. Whatever view one takes of the broader US campaign, these boardings do not meet the legal definition of piracy.
Under UNCLOS, primary legal authority over a vessel rests with its flag state, the country where the ship is registered, which is responsible for what occurs on board. There are, however, limited exceptions. Article 110 sets out five circumstances in which a warship from any state may board a foreign vessel on the high seas: where there are reasonable grounds to suspect the vessel is engaged in piracy, the slave trade, unauthorised broadcasting, is stateless, or is falsely claiming a nationality. These exceptions exist because piracy and slavery are treated as offences of universal concern, allowing any state to intervene regardless of the vessel’s flag.
The question of statelessness is central to the recent US boardings. Under UNCLOS, any warship may board a vessel on the high seas if it is stateless, meaning it is not lawfully registered with any country or is falsely claiming a nationality. This is particularly relevant to shadow fleet vessels used to move sanctioned oil. They often operate outside normal maritime regulatory frameworks, including safety, insurance, and reporting requirements.
This appears to have been the case with several recent boardings linked to Venezuela. In one instance, a vessel falsely claimed it was Guyana-flagged. Where a vessel cannot demonstrate a genuine flag state, it may be treated as stateless and boarded under international law.
Another common feature of shadow fleet operations is the use of flags of convenience. In such cases, the flag state retains jurisdiction but in my experience will commonly authorise a boarding by another state’s warship, because they have no real connection with the vessel.
This appears to have occurred in the boarding of the tanker Centuries on 20 December 2025, when the US intercepted the vessel with the authorisation of Panama, its flag state.
A more complicated case study is the 7 January 2026 boarding of the vessel formerly known as Bella 1, now operating as Marinera in the Atlantic near Iceland, which was initially treated as stateless. When approached for boarding, the vessel refused consent and began crossing the Atlantic. During the transit, it painted a Russian flag on its hull and claimed to be registered as a Russian vessel.
Boarding vessels at sea is a routine naval activity permitted in limited circumstances under international law.
This is precisely the scenario anticipated by the drafters of UNCLOS. Article 92 makes clear that a ship may not change its flag during a voyage except in cases of a genuine transfer of ownership or formal change of registry. Simply repainting a flag or asserting a new nationality mid-voyage has no legal effect. However, as technology has allowed for the registration of vessels online at sea, there is an open question about whether it was formally registered to Russia at the time of boarding. This is in many ways a new consideration for UNCLOS and may set a precedent. On the available information, when the vessel was boarded by the US on 7 January, that boarding was likely lawful under the international law of the sea, because it was not lawfully registered.
Other aspects of the US pressure campaign on Venezuela raise serious and legitimate questions under international law.
The tanker boardings, however, rest on a different international legal footing. Their lawfulness does not derive from unilateral US sanctions or from the existence of a blockade. The US has not established a lawful naval blockade, and what is occurring is better understood in legal terms as a form of quarantine, a distinction that warrants separate and more detailed discussion.
Instead, the boardings are grounded in the law of the sea itself. UNCLOS permits the boarding of stateless vessels and allows boardings with the consent of a vessel’s flag state where jurisdiction exists. Where applicable, US sanctions and arrest warrants may follow these actions as a matter of domestic law, but they do not themselves provide the international legal basis for the boardings.
The tanker boardings appear consistent with international law, although the Bella 1 episode and its attempted reflagging at sea will likely be debated by maritime lawyers for years to come.
