When Joe Biden announced that he would be sending cluster munitions to Ukraine, UK Prime Minister Rishi Sunak wasted no time in expressing his disapproval. In fact, such was the level of dismay that the US President felt compelled to make a pit stop at Downing Street shortly before the Nato summit later that week. During the meeting, the PM was said to have “discouraged” Biden from sending the weapons, adding that the UK could not “produce or use cluster munitions”.

The UK, unlike the US, is one of over 120 countries signed up to the Convention on Cluster Munitions, which prohibits all use, production, transfer and stockpiling of the explosives. But the careful wording of Sunak’s remarks are as notable for what they don’t say as for what they do.

In fact, the UK served as a key driving force behind specific clauses in the Convention which allow signatory nations to provide training in the use of cluster munitions to allied militaries that are not parties to the CMC, and logistically support their use. From London’s perspective, this would of course include Washington and Kyiv.

A military directive covering assistance on cluster munition use surfaced in 2021, over a decade after the Convention came into force in London — and even then mistakenly, in response to Freedom of Information requests from an independent researcher. A lengthy ensuing battle to keep the information in the public domain was only successful due to the Information Commissioner’s Office intervention.

The directive reveals just how partial and incomplete the munitions ban actually is. It starts by noting that the Cluster Munitions (Prohibitions) Act 2010 “implements the Convention’s obligations in UK law”, and prohibits cluster bomb use “from taking place at all within the UK, and by all UK nationals anywhere”.

However, it goes on to state that Article 21 of the CMC, which is reflected in the Act, “enables continued international military operations and international military cooperation between signatory and non-signatory States, which might engage in activities prohibited in the Convention”. Moreover, the Act provides “legal defences for UK personnel operating with [cluster munitions] alongside allies from non-signatory states”, such as the US.

These “interoperability provisions” do not authorise the UK to “develop, produce or otherwise acquire” cluster bombs, and British military personnel may not be “part of a crew (within a cockpit) or individual weapons platform that dispenses” these munitions. However, they “ensure that NATO and other coalition operations can proceed without UK personnel being liable to prosecution for undertaking normal operational duties” if cluster munitions are used by non-signatories. 

“Normal operational duties” described in the directive are extraordinarily broad. While the UK armed forces “must not be in a position where they expressly request, or direct” the use of cluster munitions “to achieve a task”, soldiers “engaged in international military operations or international military cooperation” are able to “call for fire support” from an allied military, even if they know that will come in the form of cluster munitions. 

They can refuel and service allied “aircraft, vessels and vehicles”, and “perform logistical planning, handling, storage, maintenance and transport services” for associated materiel, which “may” include cluster bombs. They can also train allied soldiers in their use. 

So, in truth, it seems that the UK armed forces can do almost anything they like with cluster bombs — while evading legal consequences — as long as it’s someone or something else ultimately deploying them. 

Furthermore, US diplomatic cables released by WikiLeaks show that in May 2009, then-Foreign Secretary David Miliband approved a loophole that would allow cluster munitions to be stored on British territory, contrary to the Convention’s obligation. Officials in Whitehall manoeuvred to ensure this plan was concealed from Parliament, in case it “complicated or muddied” debate around the CMC. 

This loophole allows Washington to store cluster weapons as “temporary exceptions” and on a “case-by-case” basis for specific military operations. It could well be, then, that US cluster munitions currently stored on British territory will soon make their way to the frontline in Ukraine, for a “specific military operation”. 

In effect, contrary to Sunak’s lofty critical pronouncements, Ministry of Defence doctrine and UK law explicitly allow the British army to facilitate the use of cluster munitions.