According to Article 49 of the Treaty on European Union, any European state which respects the principles specified in Article 6 (1) of the Treaty ("liberty, democracy, respect for human rights and fundamental freedoms, and the rule of law") may apply to become a member of the EU.
With the accession of Bulgaria and Romania on 1 January 2007 the EU grew to include 27 Member States. But the enlargement process is continuing:
In June 1993, the Copenhagen European Council spelt out the conditions for EU membership known as the Copenhagen Criteria. These require that candidate countries have:
"The Union's capacity to absorb new members, while maintaining the momentum of European integration, is also an important consideration in the general interest of both the Union and the candidate countries." The European Commission for the first time focused more on the EU's ability to integrate new members in its special report on the Union's capacity to integrate new members, which was annexed to the Strategy Paper of 8 November 2006.
The Luxembourg European Council of December 1997 determined that compliance with the Copenhagen political criteria was a prerequisite for the opening of any accession negotiations. By contrast, the economic criteria and the ability to fulfil the obligations arising from membership (acquis criterion) were to be assessed in a "forward-looking, dynamic way".
In accordance with Article 49 of the EU Treaty, countries desiring membership to the Union must address their applications to the Council. The latter acts unanimously after consulting the Commission and receiving the assent of the European Parliament, which acts by an absolute majority of its members.
Before the Council makes a decision on the application, accession negotiations must take place. In these negotiations the conditions of admission and the adjustments to the Treaties on which the EU is founded entailed by the new admission are laid down in an agreement between the Member States and the applicant State. The accession negotiations may last several years and are only opened once the Commission has thoroughly examined the application and made a recommendation to this effect. The accession treaty must be ratified by all Member States and by the candidate.
The negotiations are conducted in an Intergovernmental Conference involving all EU Member States and the respective candidate State, and decisions are taken unanimously.
The EU pre-accession strategy comprises a package of measures and agreements designed to help the candidate countries to prepare for accession to the Union: