The Treaty of Lisbon provides for a mechanism for voluntary and unilateral withdrawal from the European Union (Article 50 of the Treaty on European Union). A Member State wishing to withdraw notifies its intention to the European Council, which provides guidelines for the conclusion of an agreement setting out the arrangements for its withdrawal.
This agreement is concluded on behalf of the European Union (EU) by the Council, acting by qualified majority, after obtaining the consent of the European Parliament.
The Treaties cease to apply to the State in question from the date of entry into force of the agreement, or within two years after notification of the withdrawal. The Council may decide to extend that period.
Any State which has withdrawn from the EU may apply to rejoin by undergoing the accession procedure once again.