"NATO did not have the backing of the United Nations Security Council to use force in Yugoslavia. Further, NATO did not claim that an armed attack occurred against another state. However, its advocates contend that NATO actions were consistent with the United Nations Charter because the UN Charter prohibits unprovoked attacks only by individual states. The principal legal issue remains, however, since NATO as such is not a member state of the UN, whether the member states of NATO, the United States and the European powers that sent armed forces to attack as part of the NATO bombing campaign, violated the UN Charter by attacking a fellow UN member state: (1) in the absence of UN Security Council authorization, and (2) in the absence of an attack or a threat of imminent attack on them. "
https://en.wikipedia.org/wiki/Legitimacy_of_the_NATO_bombing...
Probably somewhere in Beijing and Moscow on the same day when bombing started, they were opening bottle of champagne because they got "excuse" to do same later when they need it.