The Use of Cluster Munitions by Saudi Arabia in Yemen and the Responsibility of the United Kingdom

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In December 2016, after repeated denials, Ahmed Asiri, a spokesman for the Saudi-led coalition fighting in Yemen, said: ‘It has become apparent that there was limited use by the coalition of the UK-manufactured BL755 cluster munition in Yemen’. This admission opened up questions about the United Kingdom’s potential responsibility for the use of cluster munitions by the Kingdom of Saudi Arabia. Britain’s Defence Secretary Michael Fallon informed the Commons that the munitions used by Saudi Arabia had been delivered in the 1980s, well in advance of the entry into force for the United Kingdom of the Convention on Cluster Munitions (‘the Convention’) on 1 November 2010. The treaty was implemented through the Cluster Munitions (Prohibitions) Act 2010 (‘the Act’).

 A judicial review of the granting of export licences to Saudi Arabia is currently taking place in the English High Court, following an application by the Campaign Against the Arms Trade (see here). The application focuses on export licences for weapons in general, and follows allegations of violations of international humanitarian law by Saudi Arabia, including, but not limited, its use of cluster munitions.

In this post, I focus on the specific responsibility of the UK arising under the Convention on Cluster Munitions for the use by Saudi Arabia of UK-provided aircraft, and support by British personnel.

The post addresses three issues: first, whether issuing export licences for aircraft to Saudi Arabia can be construed as a breach of Article 1(c) of the Convention; second, whether the exception on interoperability in Article 21 of the Convention covers the acts by the UK in respect to the use of cluster munitions by Saudi Arabia; and third, whether the UK’s responsibility could also arise also under Article 16 of the Draft Articles on the Responsibility of States for Internationally Wrongful Acts (‘the 2001 Articles’).

Export Licences for Aircraft and the Prohibition of Assistance under Article 1(c) of the Convention

The first issue is whether the sale of aircraft can be construed as a breach of the Convention. Before developing the legal argument, it is paramount to assess what evidence is available for this claim. The cluster munitions whose use has been confirmed by both the Saudi and UK governments are UK-made BL755, manufactured by Hunting Engineering Ltd since 1972. These munitions are cleared for use with the BAE-made Tornado aircraft. BL755 cluster munitions cannot be deployed without aircraft. In a reasonable analogy, they are like bullets which need pistols to be delivered.

Following a request under the Freedom of Information Act (2000) that I made on 10 January 2017, the Ministry of Defence (‘MoD’) confirmed that:

  • The UK signed an export licence for Tornado aircraft in 1998 (a follow-up question on whether further export licences were granted for other aircraft is currently pending);
  • BAE provides through-life support for all its aircraft (follow-up question on review procedure pending);
  • BAE also provides type conversion training (follow-up on whether this includes usage of munitions deployment, including sensors and radar, and frequency of training);
  • All UK support for BL755 stocks was withdrawn at end of 2008 (follow-up on timing of last refresher training and life-span of training);
  • BAE provides Tornado Release to Service (RTS) documents, which until 2008 contained carriage and release clearances for BL755 (follow-up on whether these RTS were requested back from Saudi Arabia in 2008 and replaced with new ones without BL755 clearances, and whether aircraft can be retrofitted not to deploy cluster bombs, and if so, whether this was done).

The Convention on Cluster Munitions was adopted on 30 May 2008 in Dublin; it was opened for signature on 3 December 2008 in Oslo. The UK signed on that date, and the Convention entered into force, as stated, in November 2010. Under Article 18 of the 1969 Vienna Convention on the Law of Treaties, the UK is ‘obliged to refrain from acts which would defeat the object and purpose of the treaty’ after signature and before entry into force. It is reasonable to state that the object and purpose of a treaty, normally indicated in the preamble, are given legal force in the main articles of the treaty, of which Article 1(c) of the Convention is undoubtedly an example. It therefore seems equally reasonable to consider the actions of the UK from December 2008 in order to assess potential responsibility, but more conservatively, any action from November 2010 will clearly be covered by the obligations arising under the Convention. Follow-up replies by the MoD to the FOI request will clarify the temporal element of the UK’s actions.

Article 1(c) of the Convention states as follows:

1. Each State Party undertakes never under any circumstances to:…

(c) Assist, encourage or induce anyone to engage in any activity prohibited to a State Party under this Convention.

For the purpose of the actions imputed to the UK, the relevant verb is ‘assist’. The question is thus whether the continued training support provided to Saudi Arabia for the use of Tornado and other aircraft constitutes ‘assistance’ for the purpose of Article 1(c) in the deployment of BL755 cluster munitions in Yemen. The prohibition ratione personae covers assistance ‘to anyone’, i.e. both States who are not parties to the Convention and indeed non-State actors. Saudi Arabia would fall under the first category, as it is not a party to the Convention. However, the material scope of the prohibition, i.e., the exact meaning of ‘assist’ for the purpose of the Convention, is not as clear, and it was not discussed extensively during the drafting stages. The Commentary to Article 1(d) of the 1993 Convention on Chemical Weapons, which is almost identically worded, notes that assistance:

‘can be given by material or intellectual support … but also financial resources, technological or scientific know-how or provision of specialised personnel, military instructions etc. to anybody who is resolved to commit such prohibited activities’.

It is arguable that this explanation can be extended to the almost identical language of the Convention and include in its scope the grant by the UK of an export licence that covers life-time support to be provided by BAE, and for what concerns the direct responsibility of BAE, to Sections 2(2) and 4(3)(c) of the Act, the first one incorporating the language of Article 1(c) of the Convention, and the second one extending the obligation to any bodies incorporated under the law of any part of the UK.

Assistance and Considerations of Interoperability with Coalition Partners – Article 21 of the Convention

Issues of assistance, prohibited under the Convention, intersect with issues of interoperability, defined as the ‘ability of forces … to operate jointly in the performance of a task, a mission or an operation’, which is allowed, with limitations, under the Convention at Article 21(3):

Notwithstanding the provisions of Article 1 of this Convention and in accordance with international law, States Parties, their military personnel or nationals, may engage in military cooperation and operations with States not party to this Convention that might engage in activities prohibited to a State Party.

This clause might not have immediate application for the problem under consideration, which does not necessary cover instances of interoperability or cooperation. Were it to be found, for example, that UK forces cooperated in the identification and selection of bombing targets by Saudi Arabia, that eventuality would undoubtedly engage Article 21’s criteria for lawful interoperability [though it should be noted that ‘mere participation’ is not to be considered assistance for the purpose of Article 21 – see Nystuen and Casey-Maslen, The Convention on Cluster Munitions: A Commentary (OUP 2010), 546 and also the UK’s declaration upon ratification of the 1997 Anti-Personnel Mine Ban Convention]. However, classifying the provision of aircraft and technical support as within the category of interoperability and cooperation would be problematic. Additionally, the undefined delimitation between prohibited assistance under Article 1(c) and allowed cooperation under Article 21 remains contested, and open to movement as a consequence of developments in customary humanitarian law. For example, an emergent customary prohibition on the use of cluster munitions would inevitably have repercussions on the application of Article 21, as the cooperation has to take place ‘in accordance with international law’. All the same, nothing in the Commentary to the Convention shows that the issue of provision of aircraft was raised during the drafting discussions of Article 1 or Article 21.

Complicity under Article 16 of the 2001 ILC Articles on State Responsibility

The third issue is whether responsibility would arise for the UK under the general rules of State responsibility as distilled in the 2001 Articles of the International Law Commission (ILC). The Commentary to the Convention suggests that Article 16 of the 2001 Articles might provide some insight on the interpretation of the concept of ‘assistance’ for the purpose of responsibility under Article 1(c).

Article 16 of the ILC Articles states as follows:

A State which aids or assists another State in the commission of an internationally wrongful act by the latter is internationally responsible for doing so if:

(a) that State does so with knowledge of the circumstances of the internationally wrongful act; and

(b) the act would be internationally wrongful if committed by that State.

It is clear from the language of the Article, and specifically its chapeau, that the international obligation must bind the State committing the act (‘the commission of an internationally wrongful act by the latter). Additionally, the assisting State must do so in the knowledge of the circumstances, and be itself bound by the international obligation in question. As Saudi Arabia is not a State party to the Convention, Article 16 is not applicable to the use of cluster munitions in the circumstances being examined here; therefore, Article 1(c) is lex specialis with respect to it. It is clear that Article 16 and its commentary are useful aids to interpretation, for example of the meaning of ‘assistance’, but not to the application of the wider scope of responsibility under the Convention, where responsibility attaches to acts of assistance regardless of whether the assisted State is bound by the prohibition or not.


This post has focused on the specific responsibility of the UK arising under the Convention on Cluster Munitions, both as a matter of international law and of domestic law, under the relevant 2010 Act, for the use by Saudi Arabia of UK-provided aircraft, and support by British personnel. The facts regarding UK support will need to be ascertained more fully, and hopefully the pending Freedom of Information requests will help provide clarity and support the legal argument. If and when responsibility will be established, it will become crucial to be able to work out the consequences, especially as a matter of domestic enforcement of the Act.

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Alessandra Asteriti says

April 11, 2017

Update FOI response on follow-up questions:
Dear Dr Asteriti,

Thank you for your correspondence dated 09 February 2017, in which you made the following request for information in relation to the letter sent to you on 03 February 2017:
"1. Is the life support of an aircraft ever reviewed? If so, how often?
2. What are the criteria for establishing the life support of
an aircraft?
3. How often is the training provided? Is it on-demand? Does the training cover general bomb release training, including use of sensors and radar?
4. Is the type conversion training offered for all other aircraft for which the UK might have provided an export licence, and is it offered on the same conditions as the Tornado training?
5. You say that all UK support for BL-755 stocks was withdrawn at the end of 2008. When was the last refresher training on the BL-755 conducted, and what is the 'life-span' of the training?
6. When was the last RTS document issued that covers BL-755? Were the documents withdrawn in 2008, and was a request in this regard made to the government of Saudi Arabia to return these, and new RTS documents issued?
7. Can the aircraft be retrofitted not to have the carriage and release capability for BL-755s, and if so, did the UK made any effort at all to do so?"

I am treating Questions 5 and 6 of your correspondence as a request for information in accordance with the Freedom of Information Act 2000 (FOIA).
A search for the information has now been completed within the Ministry of Defence (MOD), and I can confirm that some information within scope of your request is held.
Question 5: We do not hold records for the BL-755 refresher training provided prior to the end of 2008. UK personnel have not provided refresher training related to this munition since UK support was withdrawn at the end of 2008. There are no records held regarding the periodicity/life-span of such training, but it might be expected to be repeated within months for certain key tradesmen.
Question 6: The original Royal Saudi Air Force (RSAF) Tornado RTS was subject to continual amendment. The BL-755 capability was removed from the RTS under an amendment issued on 16 December 2008, which had an accompanying instruction to remove and destroy the affected pages. This amendment aligned with a complete re-issue of the RSAF Tornado RTS on 16 December 2008 that reflected a wide-ranging upgrade to the aircraft's systems; effectively rendering the original RSAF Tornado RTS obsolete. The re-issued RTS does not contain any material relating to BL-755.
The remainder of your request appears to fall outside the scope of the FOIA as you have not requested recorded information. However, under Section 16 of the Act (Advice and Assistance) you may find it helpful to note that the level of through-life support for platforms is reviewed with the RSAF during extensions to the current agreements for such support. This broadly happens every five years. The RSAF are advised on UK standards of support for common platforms, but determine and operate under their own policies, although MOD personnel continually assess the safety processes associated with contracted services. Aircrew training is provided on-demand to meet the schedule of the RSAF training system. It includes training on the operation of weapons, including the use of the aircraft's sensors and radar. Type training is provided for all UK-built and supplied aircraft, including the UK-supplied Typhoon and Hawk aircraft. The capability to target and release a BL-755 could be inhibited though modification of the aircraft systems, however, as the aircraft remain the sovereign property of Saudi Arabia, this is ultimately a matter for the RSAF.
The only UK-built aircraft licensed and delivered to the RSAF since 2008 have been Typhoon combat aircraft and Hawk Advanced Jet Trainers. These aircraft were not delivered with the capability to deploy cluster munitions; the only UK-built aircraft believed to have been operated by the RSAF in Yemen are the Tornado and Typhoon.