As I understand it, the EU27 leadership made the UK a conditional offer with various options to extend the Article 50 negotiation period. Who has to act to accept and enact the extension?

  • Can the UK government accept it on behalf of the UK or do they legally need an act of parliament first?

  • Once the UK selects one option, do the EU27 governments have to formally accept it or has this acceptance been given in advance? Do any of the EU27 governments need parliamentary approval before they can act?

  • Can this be done by phone or does it require physical letters which must be delivered and accepted?

  • 1
    It's not precisely a conditional offer. The extension until the 12th April is "free", after that there are conditions.
    – origimbo
    Mar 25, 2019 at 21:48

3 Answers 3


They need an act of parliament. Not so much because of the change in the withdrawal act, but because they made a law in the UK which mentions that the UK will leave the EU on March 29 2019. That law needs to be withdrawn or modified. It's unclear ("legal confusion" below) what happens if parliament rejects this.

The BBC has a nice graph:

Brexit: Next steps

  • 2
    It's also fantastically unlikely that they will reject it after specifically voting for an extension in the first place, and voting against a No Deal outcome.
    – Kevin
    Mar 25, 2019 at 22:31
  • 26
    Do not assume that politician's decisions or votes follow logic or are in any way consistent.
    – Aganju
    Mar 25, 2019 at 23:00
  • The legal confusion is that the UK already agreed the extension
    – Caleth
    Mar 25, 2019 at 23:29
  • So assuming that May's deal is not approved, there need to be votes in both houses (as per Alex's answer) and a letter written by the government? All in less than 78 hours from now?
    – o.m.
    Mar 26, 2019 at 5:20
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    This answer is unclear. Changing the date to match the options agreed with the EU requires a statutory instrument, not an Act, as described in Alex's answer. An Act is required to implement the Withdrawal Agreement. Other options may or may not require an Act. Mar 26, 2019 at 9:56

The European Council has already agreed to both dates so they don’t need to ratify anything any more.

A new UK Act isn’t required. The UK Government can put forward a Statutory Instrument to amend the existing Withdrawal Act. This does need to pass both Houses of Parliament but this is unlikely to be blocked.

In both cases, confirmation in writing will be given but that’s just a formality.

Which date applies depends on whether the Withdrawal Agreement bill is passed by the UK Parliament.

If it is, then a May 22nd date will apply to allow all the necessary legislation to be passed.

If not, then the UK Government will leave the European Union on April 12th unless they come to an alternative agreement before then.

  • 1
    Isn't it April 12th? Mar 25, 2019 at 21:43
  • 1
    I'm worried about the scheduling of those formalities. Votes in both houses and a letter written before noon Friday, and they won't even start until after Wednesday? Could there be accidental Brexit because someone cuts something too close?
    – o.m.
    Mar 26, 2019 at 5:23
  • @o.m. Not really - the UK leaves the EU under A50 of the Lisbon treaty, not under its own domestic law. What would happen if this didn't pass parliament would be that the UK is still in the EU but domestically would have to pretend it isn't.
    – Cubic
    Mar 26, 2019 at 16:23
  • @Cubic, the notification according to Article 50 must be in accordance to national constitutional requirements. Surely the same applies to an extension?
    – o.m.
    Mar 26, 2019 at 16:36
  • @o.m. You're right in the sense that, if they don't go through the motions, the UK leaves the EU on Friday. But it's not a big risk. It's not like they are likely to forget and they have plenty of time.
    – Alex
    Mar 26, 2019 at 17:29

Note that unilateral revocation by simple letter of the Prime Minister remains an option.

(I believe that since the Electronic Communications Act email counts as "in writing" for all cases where that is legally required. I don't know if international agreements have to be in writing because this kind of temporal brinksmanship rarely comes up)

  • 3
    That doesn't answer the question of unilateral remain, only the ratification of a withdrawal agreement.
    – pjc50
    Mar 25, 2019 at 23:43
  • 1
    @Sjoerd - My reading of your link agrees with pjc50's interpretation. I.e. that it doesn't apply to "remain"; only the requirements of a withdrawal. That's not to say that pjc50's original answer is correct (perhaps it is wrong?) but the link you've given appears to be irrelevant. Mar 26, 2019 at 7:06
  • The ECJ ruling on whether it's possible to revoke article 50 (curia.europa.eu/jcms/upload/docs/application/pdf/2018-12/…) states that "The revocation must be decided following a democratic process in accordance with national constitutional requirements. This unequivocal and unconditional decision must be communicated in writing to the European Council." IMHO a simple letter of the Prime Minister would not meet these criteria if the Parliament does not repeal the Withdrawal act.
    – Peteris
    Mar 26, 2019 at 13:27
  • @Peteris but in other people's opinions, it would. If anyone wanted to argue it, they'd have to go to the ECJ
    – Caleth
    Mar 26, 2019 at 14:05

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