Koštunica won the 2000 Yugoslav presidential election as a candidate of a wide alliance Democratic Opposition of Serbia (DOS), which led to overthrow of Slobodan Milošević and withdrawal of international sanctions against Yugoslavia. He strictly opposed the cooperation with International Criminal Tribunal for the former Yugoslavia (ICTY) and his party left the coalition government in protest of a decision to extradite Slobodan Milošević to the ICTY. After the 2003 Serbian parliamentary election, the first elections after the dissolution of DOS and assassination of Prime Minister Zoran Đinđić, Koštunica formed the minority government with the support of the Milošević's Socialist Party of Serbia and became the head of government. He was one of the crucial figures for the adoption of the first constitution of an independent Serbia, as well as for declaring Serbia a neutral country. During his second government (2007-2008), he opposed signing the Stabilisation and Association Agreement (SAA) with the European Union, leading to the fall of the government after a year and the early elections won by pro-European parties.