A 🧵on some legal issues arising out of the US strike on Iran’s nuclear installations: ⬇️ 1               The inherent right to use force in the face of an imminent attack from a hostile nation is well-established in international law and for good reason: a country cannot be expected to remain idle and wait until it is actually attacked.   2               Iran has repeatedly threatened to attack the UK’s bases and personnel if the UK ‘assists’ Israel, with no clarity as to what Iran deems or might deem to be ‘assistance’, nor the scale of its intended attack. Those threats come in the context of a persistent Iranian threat to life on UK soil, too; the Director General of MI5 recently stated that since the start of 2022 the UK has responded to 20 Iran-backed plots, presenting potentially lethal threats to British citizens and UK residents. There is also a constant barrage of cyberattacks; while not all cyberattacks are armed attacks in the sense of Article 51 of the UN Charter, some may be, and all confirm not just hostile intent but action pursuant to such intent.   3               The UK’s long-standing ally, Israel, was right to consider that it faced an imminent attack prior to its recent military action, given that (i) Iran has previously attacked Israel both directly and through proxies; (ii) Iran has repeatedly stated its intent to destroy Israel; (iii) Iran was assessed to be on the brink of acquiring a nuclear capability with uranium enrichment at 60% (which can only be for military use); and (iv) Iran already possessed – as demonstrated by its recent attacks – a sophisticated and effective long-range delivery capability which Israel cannot fully neutralise with defensive weapons.   4               The acquisition of a nuclear capability by Iran represents a genocidal risk for Israel and its people. Iran’s repeatedly stated aim is to wipe the State of Israel, and its inhabitants, off the face of the earth. The slogan of the proxies through which Iran has often attacked Israel is: “God is greater, death to America, death to Israel, curse to the Jews, victory to Islam”. In these circumstances, whether they are characterised as part of an ongoing armed conflict with Iran or as a new use of force based on self-defence, Israel’s actions are justifiable.   5               The UK is permitted under international law to use force to aid another State which is acting in self-defence. Moreover, the UK is under an obligation in international law is to prevent genocide, not just to stop it: stopping an on-going genocide is required, but it necessarily means that action was taken too late.   6               Against that background, the UK has three distinct legal bases to assist, militarily if necessary, its long-standing allies the US and Israel: (1) to defend another member state pursuant to collective self-defence; (2) to take proportionate action to avert Iranian attacks on the UK’s own bases and personnel; and/or (3) to prevent Iran from implementing its clearly stated genocidal intentions against the people of Israel.   7               @Keir_Starmer’s statement welcomed the effect of the US military action in destroying much of Iran’s nuclear program, but is notably silent on its legality, a silence no doubt attributable to his @attorneygeneral who, reportedly, has (unspecified) legal concerns.   8               The US and the UK are in the same legal position; accordingly, if the UK Govt’s position (as reported) is that the UK cannot itself take offensive military action to support Israel, the UK Govt must also consider that the US strike on Iran’s nuclear reactors was illegal. 
The UK Govt cannot welcome the ends but prevaricate about the means. So: what is our Govt’s stance on the legality of the US military action. I support it. Does @Keir_Starmer?