The final decision on the mission was planned to be taken on 28 January 2008. This was postponed due to concerns over possible negative effects on the second round of the presidential election in Serbia on 3 February 2008 and the possible signing of the Stabilization and Association Agreement with Serbia on that date. The officially voiced reason for the postponement is the lack of a legal basis (through a UNSC resolution or something similar) for the mission. A Joint Action was approved on 4 February 2008 and the final decision was made on 16 February 2008. A joint action is a method of implementing the Common Foreign and Security Policy, and are binding on member states.
Spain does not take part in EULEX mission, since legal questions over how it replaces the UN administration have not been answered. In June 2008, Spanish Foreign Minister Miguel Ángel Moratinos told a meeting of European Union Foreign Ministers in Slovenia that Spain will not send its contingent to the EULEX mission until there has been a formal transfer of powers from the United Nations.
Apart from EU members, third parties Croatia, Turkey, Switzerland, Norway, Canada and the United States also take part.