United Kingdom invocation of Article 50 of the Treaty on European Union

The British government stated that they would expect a leave vote to be followed by withdrawal, not by a second vote.[7] In a leaflet sent out before the referendum, the British government stated "This is your decision. The Government will implement what you decide."[8] Although Cameron stated during the campaign that he would invoke Article 50 straight away in the event of a leave victory,[9] he refused to allow the Civil Service to make any contingency plans, something the Foreign Affairs Select Committee later described as "an act of gross negligence".[10]

Unlike the Parliamentary Voting System and Constituencies Act 2011, which contained provisions for an "alternative vote" system which would have become operative only if approved by the voting result in the referendum held under the Act,[11] the European Union Referendum Act 2015 did not state that the government could lawfully invoke Article 50 without a further authorising Act of Parliament.

Following the referendum result, Cameron announced before the Conservative Party conference that he would resign by October, and that it would be for the incoming prime minister to invoke Article 50.[12] He said that "A negotiation with the European Union will need to begin under a new Prime Minister, and I think it is right that this new Prime Minister takes the decision about when to trigger Article 50 and start the formal and legal process of leaving the EU."[13]

After a court case, the government introduced a bill that was passed as the European Union (Notification of Withdrawal) Act 2017.

Article 50 provides an invocation procedure whereby a member can notify the European Council and there is a negotiation period of up to two years, after which the treaties cease to apply with respect to that member—although a leaving agreement may be agreed by qualified majority voting.[14] In this case, 20[lower-alpha 1] remaining EU countries with a combined population of 65% must agree to the deal.[16] Unless the Council of the European Union unanimously agrees to extensions, the timing for the UK leaving under the article is the mandatory period ending at the second anniversary of the country giving official notice to the EU. The assumption is that new agreements will be negotiated during the mandatory two-year period, but there is no legal requirement that agreements have to be made.[17] Some aspects, such as new trade agreements, may be difficult to negotiate until after the UK has formally left the EU.[18]

Negotiations after invoking Article 50 cannot be used to renegotiate the conditions of future membership as Article 50 does not provide the legal basis of withdrawing a decision to leave.[11]

On the other hand, the constitutional lawyer and retired German Federal Constitutional Court judge, Udo Di Fabio, has stated[19] that

• The Lisbon Treaty does not forbid an exiting country to withdraw its application for leaving, because the Vienna Convention on the Law of Treaties prescribes an initial notification procedure, a kind of period of notice. Before a contract under international law [such as the Lisbon Treaty], which had been agreed without specifying details of giving notice, can be effectively cancelled, it is required that the intention to do so is expressed 12 months in advance: in this matter there exists the principle of preserving existing agreements and international organisations. In this light, the declaration of the intention to leave would itself be, under EU law, not a notice of cancellation.
• Separate negotiations of the EU institutions with pro-EU regions [London, Scotland or Northern Ireland] would constitute a violation of the Lisbon Treaty, according to which the integrity of a member country is explicitly put under protection.

A February 2016 briefing note for the European Parliament stated that a withdrawal from the EU ends, from then on, the application of the EU Treaties in the withdrawing state, although any national acts previously adopted for implementing or transposing EU law would remain valid until amended or repealed, and a withdrawal agreement would need to deal with phasing-out EU financial programmes. The note mentions that a member withdrawing from the EU would need to enact its own new legislation in any field of exclusive EU competence, and that complete isolation of a withdrawing state would be impossible if there is to be a future relationship between the former member and the EU, but that a withdrawal agreement could have transitional provisions for rights deriving from EU citizenship and other rights deriving from EU law that the withdrawal would otherwise extinguish.[20] The Common Fisheries Policy is one of the exclusive competences reserved for the European Union; others concern customs union, competition rules, monetary policy and concluding international agreements.[21]

In oral evidence to a Select Committee of the House of Lords in March 2016, one of the legal experts (David Edward) stated that the German text of Article 50 could be taken to mean that the structure of future relations between the UK and EU will already have been established at the point when withdrawal takes place, which could be taken as a difference from the English text "the Union shall negotiate and conclude an agreement with the withdrawing state setting out the arrangements for its withdrawal and taking account of the framework for its future relationship with the Union".[22]

Nicolas J. Firzli of the World Pensions Council (WPC) argued in July 2016 that it could be in Britain's national interest to proceed slowly in the following months; Her Majesty's Government might want to push Brussels to accept the principles of a free trade deal before invoking Article 50, hopefully gaining support from some other member states whose economy is strongly tied to the UK, thus "allowing a more nimble union to focus on the free trade of goods and services without undue bureaucratic burdens, modern antitrust law and stronger external borders, leaving the rest to member states".[23]

May confirmed that discussions with the EU would not start in 2016: "I want to work with ... the European council in a constructive spirit to make this a sensible and orderly departure", she said. "All of us will need time to prepare for these negotiations and the United Kingdom will not invoke article 50 until our objectives are clear." In a joint press conference with May on 20 July, Germany's Chancellor Angela Merkel supported the UK's position in this respect: "We all have an interest in this matter being carefully prepared, positions being clearly defined and delineated. I think it is absolutely necessary to have a certain time to prepare for that."[24]

In February 2017, the Scottish Parliament voted with overwhelming majority against invoking Article 50.[25] After the British Government had nevertheless chosen to invoke Article 50, the Scottish Government was formally authorised by the Parliament by a vote of 69 to 59 to seek to hold a second Scottish independence referendum.[26]

During the referendum David Cameron stated that, "If the British people vote to leave, [they] would rightly expect [the invoking of Article 50] to start straight away",[35] and there was speculation that he would do this on the morning with Eurosceptic MPs calling for caution to assess the negotiating position[36] and Jeremy Corbyn calling for immediate invocation.[37] During a 27 June 2016 meeting, the Cabinet decided to establish a unit of civil servants, headed by senior Conservative Oliver Letwin, who would proceed with "intensive work on the issues that will need to be worked through in order to present options and advice to a new Prime Minister and a new Cabinet".[38]

Instead of invoking Article 50 Cameron resigned as prime minister, leaving the timing to a successor. There was speculation in the UK that it would be delayed,[39] and the European Commission in July 2016 believed that Article 50 notification would not be made before September 2017.[40]

Following the referendum result, Cameron announced that he would resign before the Conservative party conference in October and that it would be for the incoming prime minister to invoke Article 50:[12]

A negotiation with the European Union will need to begin under a new Prime Minister, and I think it is right that this new Prime Minister takes the decision about when to trigger Article 50 and start the formal and legal process of leaving the EU.[13]

Cameron made it clear that his successor as prime minister should activate Article 50 and begin negotiations with the EU.[6] Among the candidates for the Conservative Party leadership election there were disagreements about when this should be: May said that the UK needed a clear negotiating position before triggering Article 50, and that she would not do so in 2016, while Andrea Leadsom said that she would trigger it as soon as possible.[41]

According to EU Economic Affairs Commissioner Pierre Moscovici, Britain had to proceed promptly. In June 2016 he said: "There needs to be a notification by the country concerned of its intention to leave (the EU), hence the request (to British Prime Minister David Cameron) to act quickly."[42] In addition, the remaining EU leaders issued a joint statement on 26 June 2016 regretting but respecting Britain's decision and asking them to proceed quickly in accordance with Article 50. The statement also added: "We stand ready to launch negotiations swiftly with the United Kingdom regarding the terms and conditions of its withdrawal from the European Union. Until this process of negotiations is over, the United Kingdom remains a member of the European Union, with all the rights and obligations that derive from this. According to the Treaties which the United Kingdom has ratified, EU law continues to apply to the full to and in the United Kingdom until it is no longer a Member."[43]

An EU Parliament motion passed on 28 June 2016 called for the UK immediately to trigger Article 50 and start the exit process.[44] There is no mechanism allowing the EU to invoke the article.[45] As long as the British Government has not invoked Article 50, the UK stays a member of the EU; must continue to fulfil all EU-related treaties, including possible future agreements; and should legally be treated as a member. The EU has no framework to exclude the UK as long as Article 50 is not invoked, and the UK does not violate EU laws.[27][28] However, if the UK were to breach EU law significantly, there are legal provisions to allow the EU to cancel membership of a state that breaches fundamental EU principles, a test that is hard to pass.[29] These do not allow forced cancellation of membership, only denial of rights such as free trade, free movement and voting rights.

May made it clear that discussions with the EU would not start in 2016. "I want to work with ... the European Council in a constructive spirit to make this a sensible and orderly departure" she said "All of us will need time to prepare for these negotiations and the United Kingdom will not invoke article 50 until our objectives are clear". In a joint press conference with May on 20 July 2016, Merkel supported the UK's position in this respect: "We all have an interest in this matter being carefully prepared, positions being clearly defined and delineated. I think it is absolutely necessary to have a certain time to prepare for that."[24]

The Supreme Court ruled in the Miller case that an explicit Act of Parliament is necessary to authorise the invocation of Article 50.

The Constitution of the United Kingdom is unwritten and it operates on convention and legal precedent: this question is without precedent and so the legal position was thought to be unclear. The Government argued that the use of prerogative powers to enact the referendum result was constitutionally proper and consistent with domestic law[46] whereas the opposing view was that prerogative powers could not be used to set aside rights previously established by Parliament.[47][48][49]

Three distinct groups of citizens – one supported by crowd funding – brought a case before the High Court of England and Wales to challenge the government's interpretation of the law.[50]

On 13 October 2016, the High Court commenced hearing opening arguments. The Government argued that it would be constitutionally impermissible for the court to make a declaration that it [Her Majesty's Government] could not lawfully issue such a notification. The government stated that such a declaration [by the Court] would trespass on proceedings in Parliament, as the Court had ruled previously[51] when rejecting a challenge to the validity of the ratification of the Lisbon Treaty after the passing of the European Union (Amendment) Act 2008 but without a referendum.[52][53] Opening the case for the Plaintiffs, Lord Pannick QC told the Court that the case "raises an issue of fundamental constitutional importance concerning the limits of the power of the Executive". He argued Mrs May could not use royal prerogative powers to remove rights established by the European Communities Act 1972, which made EU law part of British law, as it was for Parliament to decide whether or not to maintain those statutory rights.[54]

On 3 November 2016, the High Court ruled[55] in R (Miller) v Secretary of State for Exiting the European Union that only Parliament could make the decision on when or indeed whether to invoke Article 50.[56] The Government's appeal to the Supreme Court took place from 5 to 8 December 2016.[57] On 24 January 2017, the Supreme Court upheld the decision of the lower court by a majority of eight to three, declaring that the invocation of Article 50 could only come by an Act of Parliament.[58][59][60] The case was seen as having constitutional significance in deciding the scope of the royal prerogative in foreign affairs.[61] The Supreme Court also ruled that devolved legislatures in Scotland, Wales and Northern Ireland have no legal right to veto the act.[62]

In February 2017, the High Court rejected a claim of several people against the Secretary of State centred on the UK's links with the European Economic Area.[63][64] However, a challenge to the notice of withdrawal continues in the courts of Scotland and in the European Court of Justice (below, "Reversibility").

On 2 October 2016, May announced that she intended to invoke Article 50 by the end of March 2017, meaning that the UK would be on a course to leave the EU by the end of March 2019.[65]

On 7 December 2016, the House of Commons approved a non-legally-binding motion supporting Article 50's invocation by 31 March 2017.[66]

As a direct consequence of the Supreme Court ruling the House of Commons voted by a majority of 384 votes (498 to 114) to approve the second reading of the European Union (Notification of Withdrawal) Act 2017 to allow the prime minister to invoke Article 50 unconditionally.[67][68][69]

On 7 March 2017 the bill passed the House of Lords, though with two amendments.[70] Following further votes in the Commons and the Lords on 13 March 2017, these two amendments did not become part of the bill, so the bill passed its final reading unamended and it received royal assent on 16 March 2017.

Invocation of Article 50 has been challenged in the British courts on the basis that the British Parliament never voted to leave the EU despite the clear decision of the Supreme Court ruling. Campaigners argue the referendum result was not ratified by an act of Parliament, which they claim means the triggering of Article 50 is invalid.[71]

According to David Davis, when presenting the European Union (Notification of Withdrawal) Act 2017: "It is not a Bill about whether the UK should leave the European Union or, indeed, about how it should do so; it is simply about Parliament empowering the Government to implement a decision already made – a point of no return already passed", further saying that the Bill was "the beginning of a process to ensure that the decision made by the people last June is honoured".[72]

In October 2016, May announced that the government would trigger Article 50 by "the first quarter of 2017".[1] She announced on Monday 20 March 2017 that the UK would formally invoke Article 50 on Wednesday 29 March 2017, meeting her self-imposed deadline.[73] The letter invoking Article 50 was signed by May on 28 March 2017,[74] and was hand-delivered on 29 March by Tim Barrow, the Permanent Representative of the United Kingdom to the European Union, to the president of the European Council in Brussels.[75][2] The letter also contained the United Kingdom's intention to withdraw from the European Atomic Energy Community (EAEC or Euratom). In response on 31 March, Tusk sent draft negotiation guidelines to the leaders of the EU to prepare for the upcoming Brexit negotiations.[76]