As Prime Minister Keir Starmer weighs up whether Britain should back the United States if Donald Trump decides to strike Iran, Attorney General Richard Hermer has reportedly warned him that UK involvement could breach international law, a question Starmer, a former human rights lawyer and vocal critic of the Iraq War, is well placed to grapple with.
As Keir Starmer considers whether Britain should support the United States should Donald Trump decide to bomb Iran, Attorney General Richard Hermer has reportedly told him that UK involvement could be unlawful. Starmer was a prominent opponent of the Iraq War back in 2003, when he worked as a human rights lawyer, and is likely to be acutely aware of the legal complications any UK role in strikes against Iran would raise.
What support could Britain actually provide?
British officials have repeatedly stressed that the UK is not expected to deploy its own armed forces in any attack on Iran. Instead, the central question is likely to be whether Britain grants permission for US B-2 stealth bombers to fly from the Diego Garcia airbase in the Indian Ocean. Diego Garcia is covered by a new 99-year lease agreement with Mauritius that leaves the UK in full operational control, even though the base is mainly used by the US military; because it remains ultimately a British base, Starmer would need to personally sign off on its use for any such attack. RAF Akrotiri, Britain’s base in southern Cyprus, represents another potential launch site for US aircraft, and any use of that base by American forces would similarly require approval from the British government.
What legal test would apply?
The United Nations Charter sets out the principles governing the lawful use of military force, recognising three possible justifications: self-defence, which can include collective self-defence; an exceptional case to avert an overwhelming humanitarian catastrophe; or authorisation from the Security Council acting under Chapter VII of the Charter. In the case of any bombing of Iran, the justification put forward by Israel, and the one likely to be echoed by the US and its allies, would be self-defence under Article 51 of the Charter. Under that provision, force may only be used in self-defence where there is an actual or imminent threat of armed attack, where it represents the only means of averting that attack, and where the force used is proportionate.
Would a US strike meet that legal test?
While the US has historically taken a broad interpretation of “imminence” in cases involving terrorism or weapons of mass destruction, it could prove difficult to characterise a US strike on Iran’s nuclear programme or leadership as self-defence against an imminent armed attack on the United States itself. The more likely argument from the White House would be that any strike was carried out in collective defence of Israel. The strength of that argument would hinge on two separate questions: whether Israel’s own attack on Iran complied with international law in the first place, and whether any US use of force was limited strictly to protecting Israeli civilians and American interests from an Iranian attack.
Is Israel’s campaign against Iran itself lawful?
Israel has said its objective is to damage Iran’s nuclear programme and prevent it from developing a nuclear weapon, a broad reading of self-defence whose legality would depend heavily on demonstrating the imminence of a nuclear threat and arguing that military action represented the last available opportunity to prevent it. There is relevant historical precedent here: in 1981, the Reagan administration in the US backed a Security Council resolution condemning Israel for bombing the Osirak nuclear reactor in Baghdad, a resolution that stated the diplomatic options available to Israel “had not been exhausted.” Comments from Israeli officials have also complicated the self-defence rationale for the current campaign. Israel’s defence minister, Israel Katz, said on Tuesday that its purpose was “to remove threats to the state of Israel and undermine the ayatollahs’ regime,” a framing that extends well beyond preventing an imminent attack.
Could Britain be held responsible for simply helping?
Under international law, there is no clear distinction between a state that carries out an unlawful attack and a state that assists it, provided the assisting state has, in the UN’s words, “knowledge of the circumstances of the internationally wrongful act.” Britain’s approach to this question has been tested before. In 2021, John Healey, now the defence secretary, pressed the then Conservative government in the Commons for clarity on the rules governing the use of British military bases by US forces, and was told any proposed operation would need to comply with UK law and Britain’s own interpretation of relevant international law. The UK’s broader position on pre-emptive strikes is well established. In the run-up to the Iraq War, the then attorney general, Lord Goldsmith, argued that international law permitted the use of force only in genuine self-defence against an actual or imminent attack, stating that the mere development of weapons of mass destruction was “not in itself sufficient to indicate such imminence”; it was only later that Goldsmith argued a separate UN resolution relating to Iraq made the war lawful. Writing in the Guardian at the time as a human rights lawyer, Starmer himself argued that Article 51 might permit a pre-emptive strike “in a nuclear world,” but only where any threat to the UK or its allies was genuinely imminent and any resulting force was proportionate, warning that “a capacity to attack at some unspecified time in the future is not enough.”
