The Use of Convoys and the Risk of Having Convoys with Combined US & Neutral Escorts

[Yiannis Bamnios is a researcher at the University of Ghent whose research focuses on the law of naval warfare. He holds an LLM in international humanitarian law and human rights from the Geneva Academy and an LLB from the Democritus University of Thrace.]

The Facts

After the U.S. and Israeli strikes on Iran on Saturday 28 February, Iran has effectively shut the Strait of Hormuz, a key shipping lane for about 20% of the world’s oil, sending global energy prices skyrocketing. Before the war, about 138 merchant vessels were passing through the Strait of Hormuz daily. So far in March, an average of 5-6 vessels per day is transiting through the Strait of Hormuz, a significant decrease. Iran’s President Masoud Pezeshkian reiterated on Sunday 22 March that crossing the Strait of Hormuz is ‘open to all, except those who violate our soil’.

In an effort to gather support to reopen the key maritime corridor, on Sunday 15 March, the U.S. President, Donald Trump, warned his NATO allies that they face a “very bad future” if they refuse to send their warships to secure the Strait of Hormuz. Most European countries, including the U.K., France and Germany, initially refused to participate, highlighting that this is not Europe’s war and that Europe will not become a party to it. 

However, on Thursday 19 March, following the adoption of UN Security Council Resolution 2817, which reaffirmed the importance of respecting navigational rights and freedoms for merchant vessels, particularly around critical maritime routes, U.S. Western allies issued a joint statement. In it, they announced their support for a potential coalition to reopen the Strait of Hormuz for commercial ships and oil tankers. The statement more likely constitutes a document of political support, while leaving the discussion on the practical steps for later. On Sunday 22 of March, Mark Rutte, NATO’s Secretary General, confirmed that 22 countries, most of them NATO, but also Japan, South Korea, Australia, New Zealand, Bahrain and UAE, have come together to make sure that the Strait of Hormuz reopens.

Regardless of how the situation evolves, President Trump’s demand raises questions on the legal status of convoys under the Law of Naval Warfare (LoNW). The issue of convoys has been discussed previously, as part of  broader LoNW issues that the war on Iran raises. The post will first outline the legal framework governing the regulation of convoys under the LoNW, before assessing which types of convoys, i.e., combinations of warships and merchant vessels, would be legally protected.

The Legal Framework

According to the rules of the LoNW, as traditionally understood, the parties to an armed conflict possess belligerent rights allowing them to undertake various measures short of attack, involving the interception, visit, search, diversion, and capture of merchant vessels (SRM, Part V). Put simply, belligerents can capture as ‘prize’ so-called ‘enemy merchant vessels’ – that is, vessels sailing the flag of the adversary at the outbreak of the conflict, as well as vessels owned by a person or company with the nationality of the enemy State. What is more, belligerents are entitled to visit and search ‘neutral merchant vessels’ to ascertain whether they carry contraband – that is, goods which are ultimately destined for enemy territory, and which may be susceptible for use in armed conflict – and if so, capture both vessel and goods alike.

A key aspect of the legal framework governing convoy formation concerns the latter belligerent right, which is how belligerent states interact with neutral merchant vessels. Convoys consist of merchant ships protected by warships, and their use carries specific legal consequences: merchant vessels may be targeted if they are escorted by non-neutral warships, while those accompanied by neutral warships are exempt from visit and search operations. The practice of convoys constitutes an effort to balance on the one hand the safety of merchant vessels and the protection of the rights of neutrals, and on the other hand, the belligerents’ interests in controlling materiel that classifies as contraband and obstructing non-neutral service.

As already said, a neutral merchant vessel is exempt from visit and search when it is escorted by a neutral warship (i.e., when sailing in convoy), including when transiting an international strait such as the Strait of Hormuz. The ratio of the rule is that warships of the parties to the conflict may control neutral merchant ships but not neutral warships. The exemption of neutral vessels from search operations if they sail under national convoys was already included in the 1909 London Declaration (Art. 61-62).

The legally critical issue of the ‘nationality’ of the convoy is determined by the flag of the escorting warships. This is important because both enemy and neutral merchant vessels under the convoy of an enemy warship are liable to attack, since they are considered as manifesting their willingness to actively resist – with the help of the accompanying warship – visit, search, and capture.

Which Convoys Would Be Legally Protected?

In order to answer this question, it is useful to consider the different types of convoy arrangements that may arise.

To begin with, the first possible scenario that one can imagine is a warship belonging to a belligerent State escorting merchant vessels. If this is the case, it is generally accepted that, under the LoNW and without prejudice to other bodies of law, the convoy is not legally protected, and therefore can be the object of an attack. However, Rule 59 of the San Remo Manual (SRM) dictates that enemy merchant vessels can only be attacked if they meet the definition of a military objective in Rule 40 SRM. While Rule 59 SRM requires that enemy merchant vessels have to satisfy the definition of a military objective under Rule 40 SRM, Rules 60(d) and 67(e) SRM clarify that escort by enemy warships is treated as evidence that both enemy and neutral merchant vessels are incorporated into the enemy’s war effort and therefore meet the Rule’s 40 criteria. In practical terms, this would mean that if a US warship is escorting a convoy of merchant vessels, either alone, or together with warships from neutral countries, for example France, this very convoy as a whole would qualify as a military target and would be liable to attack by Iran.

The picture changes if the escorting warships sail under the flag of neutral States. If, for example, a French warship were to escort a convoy of neutral merchant vessels, that would render the convoy exempt from the belligerent right of visit and search, provided certain guarantees and assurances are given (UK LOAC Manual 13.93; SRM, Rule 120; Newport Manual 9.7.1). In particular, this exemption applies only insofar as the neutral warship’s flag constitutes a guarantee that the escorted merchant vessels are neither carrying contraband nor otherwise acting inconsistently with their neutral status, and the commander of the neutral warship, if so requested by an intercepting belligerent, provides all information regarding the vessels and their cargo that would otherwise be obtained through visit and search.

The SRM and the U.S. Commander’s Handbook on the Law of Naval Operations adopt a somewhat differentiated approach regarding the nationality requirement for the merchant vessels in the abovementioned example. According to the San Remo Manual, the neutral merchant vessel must have the same nationality as the escorting warship, or an agreement must have been concluded between the warship’s flag State and the flag State of the merchant vessel. According to this view, a French warship would only be able to escort, and thus ‘shield’ from Iranian visit and search operations, French merchant vessels or merchant vessels with which France has concluded an agreement. 

This rule is not retained in the Newport Manual, while the U.S. Commander’s Handbook states that “Neutral merchant vessels under convoy of neutral warships of the same nationality are exempt from visit and search” (NWP 1.14M § 7.6). Most commentators endorse this latter view (p. 626). Consequently, the nationality of the neutral merchant vessels does not affect the status of the convoy so long as the escorting warships are themselves neutral, and no special agreement is required.

Moving forward to another possible scenario, it is beyond doubt that if merchant vessels of a party to the conflict are placed under the protection of a neutral warship, such a formation of a convoy would constitute non-neutral service. For example, in the Iran/U.S. conflict, a French neutral warship cannot escort U.S flagged merchant vessels, or any other cobelligerent’s vessels. It is worth recalling that enemy merchant vessels can traditionally be taken as ‘prize’, thus it is only logical that neutral warships cannot ‘shield’ enemy merchant vessels by functioning as escorts.

Where the situation becomes less clear is when the flag State of a neutral warship decides to reflag merchant vessels that were previously sailing under the flag of a belligerent State. This was the case during the so called ‘Tanker War’ between Iran and Iraq (1984-1987). During the naval war, the U.S. reflagged Kuwaiti oil tankers and used its warships to effectively escort them. Even though Kuwait was nominally neutral during the conflict, its support in practice for Iraq raises serious doubts on whether the disguise of non-neutral service legally ‘shields’ merchant vessels from visit and search operations. Iran expressly did not claim a right to visit and search the reflagged Kuwaiti oil tankers. However, whether the reflagging of non-neutral merchant vessels to evade visit and search operations constitutes a lawful practice, remains unsettled. 

To sum up, the only legally waterproof combination of merchant vessels and warships that would form a convoy, legally protected from Iranian actions, would be one in which both the merchant vessels and the warships are of a neutral flag State. Any involvement of U.S., Israeli or other cobelligerent’s vessels, either merchant or warships, would compromise the character of the convoy by rendering its service non-neutral. It must be noted here that the U.K.’s position to allow the use of British bases by the U.S. (see here, here and here) to, among others, stop Iranian attacks on shipping at the Strait of Hormuz, places the U.K. in a tricky situation and thus, would more likely qualify as non-neutral in the context of the Iran-U.S./Israel war.

Concluding Thoughts

The war in Iran is unfolding with remarkable speed and volatility. The decrease in the number of vessels that sail through the Strait of Hormuz on a daily basis is alarming, with the consequences of this phenomenon being felt globally. At the same time, Europeans and others should think twice before embarking on a mission to safeguard the freedom of navigation in the Strait of Hormuz. As has been examined above, if neutral warships or neutral merchant vessels co-participate in a convoy that would implicate U.S. or Israeli vessels, either as escorts or as escortees, that very convoy would constitute a lawful target for Iran in the first case or would be liable to visit and search operations in the second case. 

Photo attribution: Photo by Guru Ankam on Unsplash.