[9] 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.
[10] 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.
The Vienna Convention on the Law of Treaties states where a party wants to withdraw unilaterally from a treaty that is silent on such procedure, 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.
The agreement is to be approved by the council, acting by qualified majority, after obtaining the consent of the European Parliament.
Should a former member state seek to rejoin the European Union, it would be subject to the same conditions as any other applicant country.
On 10 December 2018, the European Court of Justice ruled that it would be “inconsistent with the EU treaties’ purpose of creating an ever closer union among the peoples of Europe to force the withdrawal of a member state” against its wishes, and that consequently an Article 50 notification may be revoked unilaterally by the notifying member without the permission of the other EU members, provided the state has not already left the EU, and provided the revocation is decided “following a democratic process in accordance with national constitutional requirements”.
[23][24][25] The European Parliament resolution of 5 April 2017 (on negotiations with the United Kingdom following its notification that it intends to withdraw from the European Union) states, "a revocation of notification needs to be subject to conditions set by all EU-27,[a] so that it cannot be used as a procedural device or abused in an attempt to improve on the current terms of the United Kingdom’s membership.
[28] Lord Kerr, the British author of Article 50, also considers the process is reversible[29] as does Jens Dammann.
[29] Extension of the two years time from notification to exit from the union, still requires unanimous support from all member countries, that is clearly stated in Article 50(3).
Instead, the European Council may, on the initiative of the member state concerned, change the status of an overseas country or territory (OCT) to an outermost region (OMR) or vice versa.
Most of these territories were not classed as part of the EU, but were at most associated with OCT status, and EC laws were generally not in force in these countries.
Later, the elected representatives of the island of Saint-Barthélemy expressed a desire to "obtain a European status which would be better suited to its status under domestic law, particularly given its remoteness from the mainland, its small insular economy largely devoted to tourism and subject to difficulties in obtaining supplies which hamper the application of some European Union standards."
[38] The UK formally left the EU on 31 January 2020, following on a public vote held in June 2016.
[39] However, the country benefited from a transition period to give time to negotiate a trade deal between the UK and the EU.
The British government led by David Cameron held a referendum on the issue in 2016; the electorate decided by a 3.8% majority to favour leaving the European Union.
[40] On 29 March 2017, arising from a decision by the Parliament of the United Kingdom, Prime Minister Theresa May invoked Article 50 in a letter to the president of the European Council, Donald Tusk.
Following a decisive election victory for Prime Minister Boris Johnson and the Conservative Party in December 2019, the UK Parliament ratified the European Union (Withdrawal Agreement) Act 2020, approving the terms of withdrawal as formally agreed between the UK government and the EU Commission.
[42] Several states have political parties represented in national assemblies or the European Parliament that advocate withdrawal from the EU.
[45] Additionally, other smaller non-parliamentary parties, mostly from the coalition Neutral Bulgaria support withdrawal, such as Attack who called the politicians who signed the treaty to join the EU "traitors.
"[46] In Czechia, the far-right Freedom and Direct Democracy opposes Czech membership of the European Union.
[47] In the Danish Parliament, the national conservative New Right party opposes Denmark's membership in the EU.
[48] The ideologically similar Danish People's Party in principle opposes EU membership, but has since 2001 in practice supported pro-EU right-wing coalitions.
[49] The left-wing Red Green Alliance which is the 3rd largest party in the country, still officially opposes EU membership,[50] but its members are divided on the issue.
Former MEP for The People's Movement Rina Ronja Kari resigned her personal membership of the Unity List.
[63] In July 2020, Italian journalist and senator Gianluigi Paragone formed Italexit, a new political party with a main goal to withdraw Italy from the European Union.
[65] In Poland, the far-right party Confederation Liberty and Independence is against the membership of the country in the European Union.
The European Council may, on the initiative of the Member State concerned, adopt a decision amending the status, with regard to the Union, of a Danish, French or Netherlands country or territory referred to in paragraphs 1 and 2.