The military involvement of the US, as well as the initial attack of Israel on Iran, seem to fly against the UN Charter and international law. The efforts of medium-sized countries like the UK to resolve the tension between Israel and Iran by diplomatic means, writes Richard Mottram, seem to have little to no influence, leaving open a future development of the conflict.

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Developments in the Israel-Iran war since Israel’s attack on June 13 have brought sharply into view that obligations under the UN Charter and international law on not using military force to seek to resolve disputes have no traction with the parties to the conflict, including the United States. Medium-sized powers like the UK committed to seeking diplomatic solutions have little or no influence, though this is not through want of effort or lack of diplomatic skill.  

This limited influence is not a new problem in respect of Iran’s nuclear programme. In 2015 six countries including the UK negotiated with Iran the Joint Comprehensive Plan of Action that restricted Iran’s holdings of enriched uranium and its purity to no more than 3.67 per cent and put in place an intrusive inspection regime. The deal was opposed by Israel and repudiated by President Trump in 2018. Whatever its faults, it seems most unlikely that had the Plan been fully implemented Iran would now have holdings of enriched uranium of the size and enrichment level to 60 per cent reported to the Board of Governors of the International Atomic Energy Agency (IAEA) on 12 June (see paragraph 80). Such a level of enrichment makes no sense for a civil nuclear programme.  

An existential threat? 

Were the developments reported by the IAEA of a kind that posed an imminent and existential threat to Israel that justified the military action by Israel and the USA we have seen? Threats are about both intent to take an action and capability to execute that intent. As to intent, since the Iranian revolution Iran’s leaders have repeatedly stated the objective of eliminating the state of Israel (often using appalling language), though the timescale in which they expect to achieve this and the means to do so have been wholly unclear.  

I have no knowledge of the assessment within the UK government of Iran’s capabilities and intentions. But the US Intelligence Community publishes an Annual Threat assessment. The March 2025 version described (page 22) how: “Tehran will try to leverage its robust missile capability and expanded nuclear program, and its diplomatic outreach to regional states and U.S. rivals to bolster its regional influence and ensure regime survival.”  

On Iranian weapons of mass destruction, there is a clear judgement (page 26): We continue to assess Iran is not building a nuclear weapon and that Khamenei has not reauthorized the nuclear weapons program he suspended in 2003, though pressure has probably built on him to do so.  

President Trump has without explanation dismissed this latter judgement as “wrong” and the Director of National Intelligence has aligned herself with the President on the basis that her previous support for this conclusion was taken out of context and Iran has enough enriched uranium to support a number of nuclear weapons within months.  

This volte-face risks calling into question the value and credibility of the huge US intelligence collection and analysis enterprise, with which the UK intelligence community is closely linked. 

Israel has never confirmed nor denied possessing nuclear weapons but its official policy of ambiguity should not affect assessment of the deterrent effect of its capability.

If hypothetically Iran achieved a nuclear weapons capability, could it credibly threaten the elimination of the state of Israel? A state facing the prospect of such an existential threat would usually seek to deter it, by, in the jargon, posing a credible capability to inflict unacceptable damage on the attacker in response to any such attack. In Israel’s case it is itself a nuclear weapons state with an estimated nuclear stockpile of around 90 warheads and a number of delivery systems. Israel has never confirmed nor denied possessing nuclear weapons but its official policy of ambiguity should not affect assessment of the deterrent effect of its capability. Why are such weapons held if not to deter Israel’s enemies? Moreover Israel has the benefit of the world’s most powerful country consistently standing behind it. The “existential threat” needs to be addressed in this wider context.  

The search for de-escalation 

On 17 June 2025 Keir Starmer told journalists at the end of G7 meeting that, after sitting next to President Trump at the G7 dinner the previous night, there was no doubt in his mind the President was serious about de-escalating the Israel/Iran conflict. 

At an emergency meeting of the UN Security Council on 20 June, the UN Secretary General warned of the risks of escalation and of the need to tackle the “trust gap” over Iran’s nuclear programme through diplomacy and a credible and verifiable solution. The UK Permanent Representative to the UN set out the government’s position. Her intervention argued for restraint, supported Israel’s need to protect its security, accepted that Iran’s nuclear programme is a “significant concern”, and pointed out that military action cannot put an end to Iran’s nuclear capabilities. She ended: “Now is the time for restraint, calm and a return to diplomacy and dialogue”.   

On Sunday 22 June (Iranian time) the US attacked three Iranian nuclear sites.  

This sequence illuminates things we already knew: the difficulty in assessing how the President will act, that the UN process has no impact on US decision-making, and nor it would appear does the UK have any influence. In so far as the US has any “special relationship” internationally, evidence suggests it is with Israel. 

The legality of military action 

Under the UN Charter states are required to settle disputes peacefully, subject to, under Article 51, the inherent right of individual or collective self-defence if an armed attack occurs against a member of the United Nations. Whether and in what circumstances an imminent but not actual threat can pre-empted under international law is contested amongst legal experts. For both the United States and Israel such arguments and potential constraints are readily put aside. But the question of legality as well as of prudence weighs more heavily in the UK government’s case. Under paragraph 1.6 of the Ministerial Code Ministers have an “overarching duty to comply with the law, including international law and treaty obligations”. Past controversies over the Iraq war and the Prime Minister’s background as a former lawyer and choice of a former colleague as the Attorney General, mean that issues of legality are perhaps becoming increasingly salient, as well as more politically controversial both in domestic politics and potentially internationally were the UK to question the legal basis for the actions of other states.  

The Foreign Secretary has also been careful to stress that it is for the US government to determine whether its action was consistent with international law.

Given its support for de-escalation and perhaps for legal reasons, the UK has played no part in the military actions taken against Iran. The Foreign Secretary said in the House of Commons on 23 June that the UK government received no request from the US government to provide any support to the operation. The practical support that might have been useful was the use of Diego Garcia as a base for the US bombers used in the attack which would have required UK permission but this was not, as we have seen, essential. We can speculate whether the US decided not to make a request to avoid the embarrassment to both governments if it was refused.   

The Foreign Secretary has also been careful to stress that it is for the US government to determine whether its action was consistent with international law. This distancing is all the more notable in the context of the government’s broad effort to maintain cordial relations with the President in particular because of the stakes involved in trade issues and US support for European security. 

What next 

As of 24 June President Trump has declared victory and ordered a ceasefire between Israel and Iran. It remains to be seen how far the conflict can be contained, if, as is likely, it emerges that the military action has significantly set back but not eliminated the possibility of Iran becoming a nuclear weapons state, should she choose to seek to do so. The whereabouts of Iran’s HEU is unclear as is the extent of the damage to its reprocessing capability. Different claims on these issues within the US Intelligence community are unlikely to be resolved quickly. The attacks on Iran may well have put further at risk its continued willingness to remain within the Non Proliferation Treaty and thereby to co-operate, at least imperfectly, with IAEA monitoring. The UK can play some part in encouraging dialogue between the US and Iran in particular and through support for the IAEA; but the prospects for success rest upon the main parties engaged having an interest in long-term solutions beneficial to all. Past form suggests no grounds for optimism.   

All articles posted on this blog give the views of the author(s), and not the position of LSE British Politics and Policy, nor of the London School of Economics and Political Science.

Image credit: Rokas Tenys in Shutterstock

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