Article 50 of the Lisbon Treaty is the legal process for leaving the EU. It establishes a two-year negotiation period, after which the departing member state is no longer subject to the EU’s treaties.
The UK triggered Article 50 on 29 March 2017, which means the UK was due to leave the EU at 11:00pm on 29 March 2019.
Since then, the UK has asked for three extensions from the EU. The current Article 50 deadline is 31 October 2019 – although the prime minister wrote to the EU on 19 October requesting an extension until 31 January 2020.
Article 50 allows for either side to request an extension, but it was the UK that, on 20 March, made the first formal request for an extension.
The extension required the unanimous agreement in the European Council, the grouping of all EU heads of state and government.
There have been two extensions agreed so far. On 19 October, Prime Minister Boris Johnson wrote to Donald Tusk, president of the European Council, requesting another extension until 31 January 2020.
On 21 March 2019, the UK and the EU agreed to extend Article 50 until either 22 May, subject to MPs approving the Withdrawal Agreement, or failing that until 12 April.
After MPs rejected the deal for the third time, Theresa May wrote to President of the European Council Donald Tusk requesting an extension until 30 June 2019. The EU27 agreed two options – an extension until 1 June if the UK didn’t hold European Parliament elections – or an extension to 31 October if it did.
In September, backbenchers took steps again to legislate on an Article 50 extension. The EU Withdrawal (No.2) Act – the so-called Benn Act – states that if MPs haven’t approved a deal agreed with the EU, or leaving without a deal, by 19 October, the prime minister must send a letter to the EU seeking an extension until 31 January 2020.
On 19 October, MPs passed the Letwin amendment which made clear that MPs would withhold their approval of the Withdrawal Agreement until the Withdrawal Agreement Bill had been passed. As a result, the prime minister wrote to Donald Tusk requesting an extension until 31 January 2020. The EU must now decide whether to grant an extension – and how long for.
If the EU27 suggest an alternative date, the prime minister must agree to that – unless MPs vote to reject it.
The government needs to amend the exit date in UK law, which it can do under the EU Withdrawal Act 2018. The EU Withdrawal Act 2019 means that the UK government does not need approval votes in Parliament to make the legal change (or any future legal change) – a measure included to help speed up the extension process.
The EU27 has recognised that the UK would have the right to revoke Article 50 during the extension.
A number of senior politicians in the UK such as former Prime Minister John Major and Conservative MP Ken Clarke have suggested that the UK could buy more time by unilaterally revoking Article 50 – this might also be a way of avoiding demands from member states reluctant to grant an extension.
Until December 2017, it was not clear whether the UK could end the Article 50 process. However, the European Court of Justice (ECJ) has ruled that a member state could decide to revoke the Article 50 notification unilaterally.
However, the judgment made clear that the decision to remain in the EU should be “unequivocal and unconditional” – which would be undermined if the UK were to revoke and then immediately retrigger Article 50. But it is hard to see how the ECJ could take action against a much more ambiguous revocation.