Officials in the House of Commons Library warn that airstrikes against ISIS in Syria may be difficult to justify under international law, despite Cameron’s view that the Assad regime is illegitimate and does not need to give permission for military operations. A briefing paper prepared for Members of Parliament:
Action in Syria will be difficult to justify legally without a request for assistance from the Assad government, and it is unlikely that the West could be seen to be responding to such a request. The British Government has said that any action in Syria will comply with international law, and the most likely way to achieve this would be to claim that military action is for humanitarian purposes, using the Responsibility to Protect doctrine. This remains controversial, however, without a United Nations Security Council resolution to authorise it.