The legality of the declaration has been disputed. Serbia sought international validation and support for its stance that the declaration was illegal, and in October 2008 requested an advisory opinion from the International Court of Justice. The Court determined that the declaration did not violate international law.
As a result of the ICJ decision, a joint Serbia-EU resolution was passed in the United Nations General Assembly which called for an EU-facilitated dialogue between Kosovo and Serbia to "promote cooperation, achieve progress on the path to the European Union and improve the lives of the people." The dialogue resulted in the 2013 Brussels deal between Serbia and Kosovo which abolished all of the Republic of Serbia's institutions in Kosovo. Dejan Pavićević is the official representative of Serbia to Kosovo. Valdet Sadiku is the official representative of Kosovo to Serbia.
The Autonomous Province of Kosovo and Metohija took shape in 1945 as the Autonomous Region of Kosovo and Metohija (1945–1963) within Socialist Yugoslavia, as an autonomous region within People's Republic of Serbia. Initially a ceremonial entity, more power was devolved to Kosovan authorities with each constitutional reform. In 1968 it became the Socialist Autonomous Province of Kosovo and in 1974 new constitution enabled the province to function at every administrative level independently of its host republic within Yugoslavia. Increasing ethnic tension throughout Yugoslavia in the late 1980s amid rising nationalism among its nations eventually led to a decentralised state: this facilitated Serbian President Slobodan Milošević in effectively terminating the privileges awarded to the Kosovar assembly in 1974. The move attracted criticism from the leaderships of the other Yugoslav republics but no higher authority was in place to reverse the measure. In response to the action, the Kosovo Assembly voted on 2 July 1990 to declare Kosovo an independent state, and this received recognition from Albania. A state of emergency and harsh security rules were subsequently imposed against Kosovo's Albanians following mass protests. The Albanians established a "parallel state" to provide education and social services while boycotting or being excluded from Yugoslav institutions.
Kosovo remained largely quiet through the Yugoslav wars. The severity of the Yugoslav government in Kosovo was internationally criticised. In 1996, the Kosovo Liberation Army (KLA) began attacking federal security forces. The conflict escalated until Kosovo was on the verge of all-out war by the end of 1998. In January 1999, NATO warned that it would intervene militarily against Yugoslavia if it did not agree to the introduction of an international peacekeeping force and the establishment of local government in Kosovo. Subsequent peace talks failed and from 24 March to 11 June 1999, NATO carried out an extensive bombing campaign against FR Yugoslavia including targets in Kosovo itself. The war ended with Milošević agreeing to allow peacekeepers into Kosovo and withdrawing all security forces so as to transfer governance to the United Nations.
A NATO-led Kosovo Force (KFOR) entered the province following the Kosovo War, tasked with providing security to the UN Mission in Kosovo (UNMIK). Before and during the handover of power, an estimated 100,000 Serbs and other non-Albanians, mostly Romani, fled the province for fear of reprisals. In the case of the non-Albanians, the Romani in particular were regarded by many Albanians as having assisted federal forces during the war. Many left along with the withdrawing security forces, expressing fears that they would be targeted by returning Albanian refugees and KLA fighters who blamed them for wartime acts of violence. Thousands more were driven out by intimidation, attacks and a wave of crime after the war.