The Guardian view on parliament's role in war on Iran: MPs should vote before Britain gets sucked in | Editorial

"Sir Keir will, however, permit US use of British bases for limited defensive strikes aimed at stopping Iranian missile attacks. That is a legally clear line, but it may be politically and militarily tricky to stick to. Donald Trump and Benjamin Netanyahu's actions are reckless and unlawful. But so are Iran's strikes hitting hotels, airports and energy infrastructure across the Gulf."

"It can be legally permissible for Sir Keir to permit the use of bases on Diego Garcia or at RAF Fairford for defensive strikes to prevent ongoing attacks. But allowing those bases to support a prolonged bombing campaign aimed at destroying Iran's wider military capability would amount to joining illegal US-Israeli actions."

"If missiles are being launched, shooting them down or hitting the launcher to stop further attacks can be lawful defensive action. But this is clearly not what Washington is talking about. Mr Trump's objectives are destroying Iran's missile capabilities and annihilating their navy, as well as preventing Tehran from ever having nuclear weapons."

Britain's Prime Minister Sir Keir Starmer has established a clear legal boundary regarding Iran: the UK will not participate in offensive operations or regime change attempts, but will allow US forces to use British bases for limited defensive strikes to counter Iranian missile attacks. This distinction between defensive and offensive action is legally sound but politically and militarily complex. While Iran's strikes on infrastructure across the Gulf and US-Israeli actions are deemed reckless and unlawful, Britain retains the legal right to act in collective self-defence where allies request support or UK nationals face risk. However, this right extends only to halting immediate attacks. Defensive measures like shooting down missiles or striking launchers to prevent further attacks are lawful, but prolonged bombing campaigns aimed at dismantling Iran's broader military capacity would constitute illegal offensive action. The UK government must ensure its stated position against offensive involvement is reflected in actual operations.

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