Seizure of the M/V Rwabee Was Consistent with International Law


| Jan 10, 2022

M/V Rwabee

On January 2, 2022, the United Kingdom Maritime Trade Operations (UKMTO) advised that Houthi rebels attacked and seized the M/V Rwabee, an Emerati-flagged cargo ship 23 nautical miles (nm) west of Yemen’s Ras Isa Marine Terminal. The incident provoked a series of legal characterizations of the event, many of which are flawed.

According to the Saudi-led coalition, the ship was transporting hospital equipment from a shuttered field hospital on Yemen’s Socotra Island to the Saudi Arabian city of Jazan. The Iranian-backed Houthi rebels alleged that the vessel was carrying military equipment, including weapons and ammunition, and had illegally entered Yemeni territorial waters without authorization. The rebels further alleged the vessel was engaged in “hostile acts targeting the security and stability of the Yemeni people.” The Saudi-led coalition, which includes the United Arab Emirates (UAE), has been battling the Houthi militia for nearly seven years in support of the internationally recognized government of Yemen.

Characterization as “Piracy”

A coalition spokesman labelled the attack an “act of piracy” and indicated that coalition forces would take “all necessary measures and procedures to handle this violation, including the use of force if necessary,” unless the Houthis immediately released the vessel. The coalition’s characterization of the attack as an “act of piracy” is misplaced. Piracy is defined in article 101 of the United Nations Convention on the Law of the Sea (UNCLOS) to include:

any illegal acts of violence or detention, or any act of depredation, committed for private ends by the crew or the passengers of a private ship…, and directed: (i) on the high seas, against another ship…, or against persons or property on board such ship…; (ii) against a ship…, persons or property in a place outside the jurisdiction of any State.

Although the UKMTO warning indicates that the attack occurred 23 nm west of the Yemeni coast, which would be considered “high seas” for purposes of article 101 (see UNCLOS articles 58.2, 86), the M/V Rwabee appears to have been operating within the Yemeni 12-nm territorial sea just north of the Zubayr island group. Therefore, given its location, the seizure of the vessel does not constitute “piracy” under international law, but rather would be considered “armed robbery at sea” in peacetime. Nonetheless, the seizure of the UAE cargo ship could be considered a violation of Yemeni domestic law.

The Houthi justification for the attack and seizure of the M/V Rwabee is likewise misplaced, as it appears to be based on a misunderstanding of the rules applicable to foreign ships engaged in innocent passage through the territorial sea. Article 25 of UNCLOS allows a coastal state to take necessary steps in its territorial sea to prevent passage of a foreign ship that is not innocent. Passage is considered “innocent” so long as it is not prejudicial to the peace, good order, or security of the coastal state.

The Houthi spokesman indicated that the M/V Rwabee was transporting military equipment through the territorial sea without permission and had therefore engaged in a hostile act that was prejudicial to the security and stability of Yemen. UNCLOS Article 19 contains an exhaustive list of activities considered to be prejudicial to the peace, good order, or security of the coastal state—the carriage of military equipment is not included in that list and would therefore not be prejudicial per se. Additionally, the Houthis are an organized armed group, not a nation state. Therefore, they do not have the legal capacity under international law to terminate non-innocent passage of a foreign ship.

Effect of Armed Conflict

Given the ongoing internal conflict in Yemen, reliance on peacetime rules applicable to piracy and the right of innocent passage to condemn or justify the attack on the M/V Rwabee is unnecessary. When a non-international armed conflict (NIAC) occurs within the territory of a single State, the parties to the NIAC may conduct hostilities in that State’s internal waters and territorial sea if they do not interfere with the right of innocent passage of other States. A State party to a NIAC, however, could temporarily suspend innocent passage, at least in those parts of the territorial sea controlled by or off the territory controlled by the rebels.

Customary international law also does not prohibit the participants in a NIAC from engaging in hostilities against each other on the high seas if they take due regard for the rights of other States. Thus, even if the attack on the UAE vessel occurred beyond the territorial sea, it would not be considered “piracy.” Moreover, by acting as a naval auxiliary for the coalition, the M/V Rwabee is considered a lawful military objective as that term is defined in Additional Protocol I, article 52.2.

During an armed conflict, an enemy merchant vessel is not entitled to a right of innocent passage and is subject to capture wherever located beyond neutral territory (see DoD Law of War Manual, paragraph 13.5.1). Enemy merchant vessels like the M/V Rwabee, which are acting in the capacity of a naval auxiliary to an enemy’s armed forces by transporting military equipment, may be attacked and destroyed with or without prior warning (see DoD Law of War Manual, paragraph 13.5.2). The same rules apply in both a NIAC and an international armed conflict. The U.S. condemnation of the seizure, which indicates that the Houthis’ “actions interfere with freedom of navigation in the Red Sea and threaten international trade and regional security,” appears to ignore the existence of the NIAC and that the M/V Rwabee was acting in the capacity of a naval auxiliary for the coalition.

The M/V Rwabee incident illustrates both the growing capacity and relevance of non-State actors at sea during NIAC, but also the importance of careful and accurate legal characterizations of their operations.


Professor Raul (Pete) Pedrozo is the Howard S. Levie Professor on the Law of Armed Conflict, U.S. Naval War College, Stockton Center for International Law.