Although states have recently agreed that there is a universal responsibility to undertake humanitarian intervention to protect populations from egregious violations of human rights, it is unclear who exactly in the international community should intervene. One option, favoured by many, is that intervention should be undertaken by those interveners whose action would be legal according to current international law. This article considers this option by assessing the moral importance of an intervener's legal status. I begin by suggesting that according to the current international law on humanitarian intervention, UN Security Council authorisation is required for an intervener's action to be legal. Then, in the main part of the article, I critically examine four reasons for treating an intervener's legal status as morally significant. Specifically, I argue that it is significantly less morally important that an intervener have UN Security Council authorisation, and therefore be legal, than is commonly assumed.