Article 50

Article 50 is a clause in the European Union's (EU) Lisbon Treaty that outlines the steps to be taken by a country seeking to leave the bloc voluntarily. Invoking Article 50 kick-starts the formal exit process and serves as a way for countries to officially declare their intention to leave the EU.

British Prime Minister Theresa May became the first leader to invoke Article 50 on March 29, 2017, following British voters' decision to pursue Brexit – the UK's exit from the EU – in a referendum on June 23, 2016. Wrangling in the courts and Parliament slowed the process down, but the government kept to its original timeline of triggering Article 50 by the end of March 2017.

The European Union began in 1957 as the European Economic Community, which was created to foster economic interdependence among its members in the aftermath of World War II. The original bloc comprised six European countries: the Netherlands, France, Belgium, West Germany, Luxembourg and Italy. These were joined by the UK, Denmark and Ireland in 1973. The EU was formally created by the Maastricht Treaty in 1992, and by 1995 the bloc had expanded to 15 members covering the whole of Western Europe. From 2004 to 2007, the EU experienced its largest-ever expansion, taking on 12 new members that included former Communist states.

Following this enlargement, the Lisbon Treaty was drafted "with a view to enhancing the efficiency and democratic legitimacy of the Union and to improving the coherence of its action." The treaty was signed and ratified by all 27 member states in 2007 and came into effect in 2009. The treaty is divided into two parts: the Treaty on European Union (TEU) and the Treaty on the Functioning of the European Union (TFEU). It has 358 articles in total.

Article 50 of the Lisbon Treaty outlines the provisions under which a country can leave the EU. Below is the text of the article:

1. Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.
2. A Member State which decides to withdraw shall notify the European Council of its intention. In the light of the guidelines provided by the European Council, the Union shall negotiate and conclude an agreement with that State, setting out the arrangements for its withdrawal, taking account of the framework for its future relationship with the Union. That agreement shall be negotiated in accordance with Article 218(3) of the Treaty on the Functioning of the European Union. It shall be concluded on behalf of the Union by the Council, acting by a qualified majority, after obtaining the consent of the European Parliament.
3. The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.
4. For the purposes of paragraphs 2 and 3, the member of the European Council or of the Council representing the withdrawing Member State shall not participate in the discussions of the European Council or Council or in decisions concerning it.
A qualified majority shall be defined in accordance with Article 238(3)(b) of the Treaty on the Functioning of the European Union.
5. If a State which has withdrawn from the Union asks to rejoin, its request shall be subject to the procedure referred to in Article 49.

The author of the provision did not originally see it as being necessary. "If you stopped paying the bills and you stopped turning up at the meetings, in due course your friends would notice that you seemed to have left," the Scottish peer Lord Kerr of Kinlochard told the BBC in November 2016. He saw Article 50 as being potentially useful in the event of a coup, which would lead the EU to suspend the affected country's membership: "I thought that at that point the dictator in question might be so cross that he'd say 'right, I'm off' and it would be good to have a procedure under which he could leave."

Article 50 became a subject of serious discussion during the European sovereign debt crisis of 2010 to 2014, when Greece's economy appeared to be spiraling out of control. In an attempt to save the euro and perhaps the EU from collapsing, leaders considered expelling Greece from the eurozone. The problem they encountered with Article 50 was that there was no clear guidance for pushing a member state out against its will. Nor was it necessary to remove Greece from the EU – just from the eurozone. Greece was eventually able to reach agreements with its EU creditors.

On June 23, 2016, a majority of British voters chose to leave the EU in a referendum, largely in response to a series of destabilizing economic events that befell the EU from 2007 to 2016. Britain's exit, popularly known as Brexit, would be the first example of a member state leaving the bloc by means of Article 50 (Algeria left the EEC following its independence from France in 1962; Greenland, an autonomous Danish territory, left through a special treaty in 1985).

Britain's Supreme Court ruled in November 2016 that Parliament must approve the triggering of Article 50, which Prime Minister Theresa May's government had intended to do through the royal prerogative. The government's bill met with challenges in the House of Lords, where peers in March added one amendment requiring Parliament's approval for a final deal and a second allowing EU nationals living in Britain to remain in the country. The House of Commons removed both amendments on March 13, sending the bill back to the upper house. The Lords deferred to the elected chamber and passed the unamended bill the same day. It received royal assent and became law on March 16.

May had promised to trigger Article 50 by the end of March 2017. The prospect of legislative "ping-pong" between the Lords and Commons led to fears that the deadline would be pushed back, the government delivered formal notification to Brussels on March 29.

After notification, the UK and the other states have a two-year window in which to negotiate a new relationship. The negotiations will almost certainly be challenging, and not just because Article 50 has never been triggered before. Three million EU nationals live, work and study in the UK, while 2 million UK nationals do same in the rest of EU. An amendment to the Article 50 bill added by the House of Lords would have allowed EU nationals to stay in the UK, but it did not survive.

In addition to migration, Britain must work out what relationship it will have with the EU's single market. May has ruled out continued membership but pushed for "the greatest possible access to it through a new, comprehensive, bold and ambitious free trade agreement." Britain and the EU will also have to work out a host of details related to pensions, security cooperation and regulations.

Since a number of other EU member countries have domestic anti-EU movements similar to Britain's UKIP, which arguably maneuvered former Tory Prime Minister David Cameron into calling the referendum, the EU has a strong incentive to offer Britain a bad deal and demonstrate that leaving is not an attractive option.

Assuming a final settlement is agreed upon, the UK will no longer be part of the EU. It will also lose access to the trade deals it enjoyed with 20-plus third countries through the EU free trade agreements.

If no agreement is reached within the two years, the UK and EU members must unanimously agree to extend the deadline, or the UK will depart without an agreement. That is what is commonly referred to as a 'Hard Brexit'. In that case, it would most likely revert to World Trade Organization (WTO) rules, though even that option is not cut-and-dry: Britain is a WTO member through the EU, and the details of independent membership would need to be worked out, such as how to apportion tariff-rate quotas.

It is not yet clear who would have to approve a final deal. In Britain, the Liberal Democrats are pushing for a second referendum on the final deal, in which the options would be to accept the terms or remain in the EU – effectively un-triggering Article 50, which may or may not be possible. A second referendum appears unlikely, but in March 2017 the Lords passed an amendment requiring Parliament's approval for a final deal. May had promised a Parliamentary vote on the deal, but the government did not include language to that effect in the Article 50 bill. The Conservative-controlled Commons stripped the Lords' amendment, and the Lords gave in and passed the unamended bill.

Whether May will follow through with the promise of a Parliamentary vote is uncertain. There is a chance that court challenges could re-insert Parliament into the approval process, as happened in November.

Nor is it certain who will have to approve the final deal on the European side. Article 50 mentions a "qualified majority" of the European Council, defined as at least 72% of the members representing at least 65% of the bloc's population. But if, as seems likely, the deal constitutes a "mixed agreement" – one in which both the EU and individual member states are affected – all member states will have to give their assent. Philip Hammond, who was foreign secretary at the time, said in July 2016 that ratification by 27 national parliaments could take around four years, or six years altogether.

After leaving the bloc, the only way for the UK to regain EU member status would be to apply again.