The European Union EU is a political and economic union of 27 member states that are party to the EU's founding treaties , and thereby subject to the privileges and obligations of membership. They have agreed by the treaties to share their own sovereignty through the institutions of the European Union in certain aspects of government. State governments must agree unanimously in the Council for the union to adopt some policies; for others, collective decisions are made by qualified majority voting.
These obligations and sharing of sovereignty within the EU sometimes referred to as supranational make it unique among international organisations, as it has established its own legal order which by the provisions of the founding treaties is both legally binding and supreme on all the member states after a landmark ruling of the ECJ in A founding principle of the union is subsidiarity , meaning that decisions are taken collectively if and only if they cannot realistically be taken individually.
Each member country appoints to the European Commission a European commissioner. The commissioners do not represent their member state, but instead work collectively in the interests of all the member states within the EU. The remaining states have acceded in subsequent enlargements.
To accede, a state must fulfil the economic and political requirements known as the Copenhagen criteria , which require a candidate to have a democratic government and free-market economy together with the corresponding freedoms and institutions, and respect for the rule of law. Enlargement of the Union is also contingent upon the consent of all existing members and the candidate's adoption of the existing body of EU law, known as the acquis communautaire.
The United Kingdom , which had acceded to the EU's predecessor in , ceased to be an EU member state on 31 January , in a political process known as Brexit. No other member state has withdrawn from the EU and none has been suspended, although some dependent territories or semi-autonomous areas have left.
