The legitimacy under international law of the 1999 NATO bombing of the Federal Republic of Yugoslavia has been seriously questioned. The UN Charter is the foundational legal document of the United Nations (UN) and is the cornerstone of the public international law governing the use of force between States. NATO members are also subject to the North Atlantic Treaty, but its use of force provision is superseded by the non-derogable prohibition of the use of force contained in the Charter, which allows only two exceptions: action taken by the Security Council under Chapter VII, and self-defence against an armed attack. Neither of these exceptions were fulfilled in this case.