Article 49 of the Maastricht treaty (European union treaty) says that any European state that respects the "principles of liberty, democracy, respect for human rights and fundamental freedoms, and the rule of law", may apply to join the Union. The Copenhagen European Council set out the conditions for EU membership in June 1993 in the Copenhagen Criteria The Western Balkan states had to sign Stabilization and Association Agreements before either applying for and gaining candidate status, and all have already done so.
It was say that no country will enter the Europe Union until the treaty of Lisbon was approved, but recently a membership was give to Iceland. So there are still some candidates Croatia that apply for consideration in 2003 and it is say it is going to enter in 2010 that if the Lisbon treaty is approved, also we have Macedonia and Turkey.