Many aspects of the Libyan situation remain unclear: the scope of the mandate given to UN member states by Security Council Resolution 1973, the broader aims of the intervention, how many civilians have been killed and by whom, and who the rebels represent. One thing, however, seems clear: the international intervention is considered to be legal. International lawyers have agreed with the UK government’s advice that Security Council Resolution 1973 ‘provides a clear and unequivocal legal basis for the deployment of UK forces and military assets to achieve the resolution’s objectives’. Legal experts have been quick to suggest that Resolution 1973 gives authority for any action thought necessary not only to protect civilians, but to protect areas inhabited by civilians. The constraints imposed on Libyan forces are similarly radical and far-reaching, going well beyond the obligations imposed by general international law on governments responding to insurgencies. The resolution demands ‘the immediate establishment of a ceasefire and a complete end to violence’, and bans all flights in Libyan airspace unless their sole purpose is ‘humanitarian’. If the expansive authority granted to international forces and the novel obligations imposed on Libya by Resolution 1973 are sanctioned by international law, what kind of law is this? And does it deserve our fidelity?