The legitimacy under international law of the 1999 NATO bombing of the Federal Republic of Yugoslavia has been 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.
Supporters of the bombing argued that the bombing brought to an end the ethnic cleansing of Kosovo's Albanian population, and that it hastened (or caused) the downfall of Slobodan Milošević's government, which they saw as having been responsible for the international isolation of Yugoslavia, war crimes, and human rights violations.
Critics of the bombing have argued that the campaign violated international law. Some also argued that NATO triggered or accelerated the ethnic cleansing in Kosovo as the violence escalated once the campaign began.
Legal justifiability of launching the war
The laws of public international law that determine whether launching a war is legally justified are called jus ad bellum.
NATO's argument for the bombing's legitimacy
NATO described the conditions in Kosovo as posing a risk to regional stability. As such, NATO and certain governments asserted they had a legitimate interest in developments in Kosovo, due to their impact on the stability of the whole region which, they claimed, is a legitimate concern of the Organisation.
The UN Charter
The UN Charter is legally binding on all United Nations member states, including all members of NATO, because they have each signed it. Article 2(4) of the UN Charter prohibits the use of force by UN member states to resolve disputes, but with two specific exceptions to this general prohibition: The first exception is set forth in Chapter VII – the UN Security Council has the power to authorize the use of force in order to fulfill its responsibility to maintain international peace and security. In particular, Article 42 states that should the Security Council consider that measures provided for in Article 41 would be inadequate or have proved to be inadequate, it may take such action by air, sea, or land forces as may be necessary to maintain or restore international peace and security. Such action may include demonstrations, blockade, and other operations by air, sea, or land forces of Members of the United Nations. Article 51 contains the second specific exception to the prohibition on the use of force – the right to self-defence. In particular, Article 51 states that nothing in the present charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security.
NATO did not have the backing of the UN 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 UN Charter because the 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.
The United Nations considers NATO to be a "regional arrangement" under UN Article 52, which allows it to deal with matters relating to the maintenance of international peace and security as are appropriate for regional action provided that such arrangements or agencies and their activities are consistent with the Purposes and Principles of the United Nations. However, the UN policy on military intervention by regional arrangements in UN Article 53 states the Security Council can, where appropriate, "utilize such regional arrangements or agencies for enforcement action under its authority. However, no enforcement action shall be taken under regional arrangements or by regional agencies without the authorization of the Security Council."
NATO's charter
Because the NATO actions in Kosovo were taken after consultation with all members, were approved by a NATO vote, and were undertaken by several NATO members, NATO contends that its actions were in accordance with its charter. Article 4, however, is silent as to the use of force and does not discuss under what circumstances force may be authorized.
