The Treaty of Lisbon puts the present criteria for joining the European Union (EU) into the governing treaties.
Certain conditions must be met before a new country can join the EU. These conditions were set by the European Council in 1993 and are known as the “Copenhagen Criteria”. These conditions do not change. However, they will be referred to in the governing treaties. This means that they cannot be changed by the European Council and can be changed only by another change to the treaties. The conditions are:
The Treaty of Lisbon provides a process for withdrawal from the EU. No member state has withdrawn from the EU to date. Greenland (which is part of Denmark) did withdraw – a special treaty was agreed to allow this.