The legal position of the alliance is shaky. The UN Charter permits states to use force in self-defence but no serious argument exists that Yugoslavia's neighbours are under attack. The Security Council can authorise force but with Russia and China opposed this is not going to happen. The legal case for using force against Yugoslavia rests uneasily on the much-disputed principle of humanitarian intervention. In the case of atrocities within a state, it is argued, outsiders are permitted to abandon the hallowed principle of non-intervention in internal affairs and take up arms to prevent a greater evil.
Precedents go back to the nineteenth century.
In 1860 the nations of Europe approved French action to protect Maronite Christians in the Lebanon from massacre. In the more complex world of the twentieth century matters are less clear. In 1978 Vietnam invaded Kampuchea to end Pol Pot's murderous activities. In 1979 Tanzania moved into Uganda after Idi Amin ran amok. These interventions were carried out by a single state which was publicly criticised by some members of the international community but privately praised by many more.