According to international law, United Nations Secutity Council Resolution 1244, signed by all of its members (USA, UK, France, Russia...) Kosovo is province of the Republic of Serbia.
On 22 July 2010 the International Court of Justice ruled that the declaration of independence of 17 February 2008 did not violate general international law, Security Council resolution 1244 (1999) or the Constitutional Framework, because the authors of the declaration, who named themselves "representatives of the people of Kosovo" were not bound by those documents. The declaration of independence was legal.