The UK Government yesterday released a short paper on legislating for the extension of Article 50 following the UK’s formal acceptance of the extension proposed by the EU.

It notes that the Government has now laid before the UK Parliament the draft Statutory Instrument (SI) that would amend the definition of “exit day” under the EU (Withdrawal) Act 2018. The SI is two-fold: if the Withdrawal Agreement was approved by the House of Commons before 11pm on 29 March GMT, “exit day” would be 11pm on 22 May 2019; otherwise, it would be 11pm on 12 April 2019 GMT. As we explain in our blog post here, the SI is subject to the affirmative procedure and needs to be approved by both Houses of Parliament before it comes into effect.

It notes that the extension agreed by the EU and the UK is legally binding under international law (and in our view the Council decision on the extension would also be legally binding under EU law). This means that even in the unlikely event of the UK Parliament rejecting the SI on the Article 50 extension, a “cliff-edge” Brexit on 29 March 2019 should not occur as the UK would still be an EU Member State at least until 11pm on 12 April 2019 and the EU and its Member States would treat it as such.

The paper, however, acknowledges the “serious problems and uncertainty with regard to the domestic statute book” that would arise if the SI was not approved by both Houses by 11pm 29 March 2019. A large body of EU exit laws that legislates for the moment when EU law ceases to apply comes into force on “exit day”, which currently is 29 March 2019, and if not amended, would create a clash between existing EU rules and new UK rules as they would become simultaneously applicable.

In the event the UK Parliament passes the Withdrawal Agreement after 29 March 2019 or the UK proposes a course of action, different from a “no-deal” exit on 12 April 2019 (following the agreement reached with the EU on the terms of the current extension), the UK can technically request another extension, although any further delay to exit day will still require the unanimous approval of the EU27. Any subsequently agreed extension(s) would require an SI(s) to be passed to reflect the new exit date.