AbstractAgainst the background of NATO's war over Kosovo in 1999, this article deals with legal and legal-political aspects of humanitarian intervention without authorisation from the UN Security Council – an issue elucidating the foundations of international law and the role of state practice in its dynamic development. It is argued that unauthorised humanitarian intervention has no legal basis in current international law: It is incompatible with Article 2(4) of the Charter, the defence of a state of necessity is not applicable and no doctrine of unauthorised humanitarian intervention has been established under customary international law. From a legal-political perspective, the crucial question is whether to develop a doctrine of humanitarian intervention without the Security Council if necessary, or stick to the existing legal order, maintaining the Security Council as the sole authoritative organ for decision-making on humanitarian intervention, while working to make it more effective. The author favours the latter alternative. However, in the short term, an ad hoc ``emergency exit'' may be needed. The special circumstances precluding wrongfulness, such as state necessity, it is argued, are not a conceptually suitable framework for justifying humanitarian intervention. But unauthorised humanitarian intervention could be undertaken ad hoc, as a deviation from international law justified solely on moral grounds. This leaves open an option for intervention in extreme cases of human suffering, but at the same time avoids jeopardising the existing, hard-earned, international legal order and the central role of the Security Council. NATO's war over Kosovo, it is argued, was such a case of ad hoc intervention on moral grounds. The article assesses the legal-political consequences of this approach in the aftermath of NATO's bombing campaign.