Initial speculation 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", however, he stated on the morning of the referendum result that he would not do this immediately. Eurosceptic MPs called for caution to assess the negotiating position and
Jeremy Corbyn calling for immediate invocation. 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".
Conservative Party leadership election 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, and the
European Commission in July 2016 believed that Article 50 notification would not be made before September 2017. 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:
EU views 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." 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." An EU Parliament motion passed on 28 June 2016 called for the UK immediately to trigger Article 50 and start the exit process. There is no mechanism allowing the EU to invoke the article. 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. whereas the opposing view was that prerogative powers could not be used to set aside rights previously established by Parliament. 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. 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 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. 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. On 3 November 2016, the High Court ruled 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. The Government's appeal to the
Supreme Court took place from 5 to 8 December 2016. 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. The case was seen as having constitutional significance in deciding the scope of the
royal prerogative in foreign affairs. The Supreme Court also ruled that devolved legislatures in Scotland, Wales and Northern Ireland have no legal right to veto the act.
Other court cases 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. However, a challenge to the notice of withdrawal continues in the courts of Scotland and in the European Court of Justice (below, "Reversibility").
British Parliament 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. On 7 December 2016, the House of Commons approved a non-legally-binding motion supporting Article 50's invocation by 31 March 2017. 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. On 7 March 2017 the bill passed the House of Lords, though with two amendments. 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. 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".
Formal notification In October 2016, May announced that the government would trigger Article 50 by "the first quarter of 2017". The letter invoking Article 50 was signed by May on 28 March 2017, 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. 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. ==Reversibility==