Withdrawal from the European Union is the legal and political process whereby an EU member state ceases to be a member of the Union. Article 50 of the Treaty on European Union (TEU) states that "Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements".
Currently, the United Kingdom is the only former member state to have withdrawn from the European Union. The process to do so began when the UK Government triggered Article 50 to begin the UK's withdrawal from the EU on 29 March 2017 following a June 2016 referendum, and the withdrawal was scheduled in law to occur on 29 March 2019. Subsequently, the UK sought, and was granted, a number of Article 50 extensions until 31 January 2020. On 23 January 2020, the withdrawal agreement was ratified by the Parliament of the United Kingdom, and on 29 January 2020 by the European Parliament. The UK left the EU on 31 January 2020 at 23:00 GMT ending 47 years of membership.
Four territories of EU member states have withdrawn: French Algeria (in 1962, upon independence), Greenland (in 1985, following a referendum), Saint Pierre and Miquelon (also in 1985, unilaterally) and Saint Barthélemy (in 2012), the latter three becoming Overseas Countries and Territories of the European Union.
Background
The states who were set to accede to the EU in 2004 pushed for an exit right during the 2002–2003 European Convention. The acceding states wanted the option to exit the EU in the event that EU membership would adversely affect them. During negotiations, eurosceptics in states such as the UK and Denmark subsequently pushed for the creation of Article 50.
Article 50, which allows a member state to withdraw, was originally drafted by British cross-bench peer and former diplomat Lord Kerr of Kinlochard, the secretary-general of the European Convention, which drafted the Constitutional Treaty for the European Union. Following the failure of the ratification process for the European Constitution, the clause was incorporated into the Treaty of Lisbon which entered into force in 2009.
Prior to this, no provision in the treaties or law of the EU outlined the ability of a state to voluntarily withdraw from the EU. The absence of such a provision made withdrawal technically difficult but not impossible. Legally there were two interpretations of whether a state could leave. The first, that sovereign states have a right to withdraw from their international commitments; and the second, the treaties are for an unlimited period, with no provision for withdrawal and calling for an "ever closer union" – such commitment to unification is incompatible with a unilateral withdrawal. The Vienna Convention on the Law of Treaties states where a party wants to withdraw unilaterally from a treaty that is silent on secession, there are only two cases where withdrawal is allowed: where all parties recognise an informal right to do so and where the situation has changed so drastically, that the obligations of a signatory have been radically transformed.
Procedure
Article 50 of the Treaty on European Union, enacted by the Treaty of Lisbon on 1 December 2009, introduced for the first time a procedure for a member state to withdraw voluntarily from the EU. The article states that:
This provision does not cover certain overseas territories which under TFEU Article 355 do not require a full treaty revision.
Invocation
Thus, once a member state has notified the European Council of its intention to leave, a period begins during which a withdrawal agreement is negotiated, setting out the arrangements for the withdrawal and outlining the country's future relationship with the Union. Commencing the process is up to the member state that intends to leave.
The article allows for a negotiated withdrawal, due to the complexities of leaving the EU. However, it does include in it a strong implication of a unilateral right to withdraw. This is through the fact that a state would decide to withdraw "in accordance with its own constitutional requirements" and that the end of the treaties' application in a member state that intends to withdraw is not dependent on any agreement being reached (it would occur after two years regardless).
Negotiation
The treaties cease to apply to the member state concerned on the entry into force of the withdrawal agreement or, in the absence of such an agreement, two years after the member state notified the European Council of its intention to leave, although this period can be extended by unanimous agreement of the European Council.