The House of Commons is set to vote on the Withdrawal Agreement and the political declaration on the future relationship ("Brexit deal") on 11 December 2018, after a 5-day debate.

This post summarises the "meaningful vote" process and the potential outcomes of the vote.

Why is a vote needed?

The UK Government needs parliamentary approval of the Brexit deal before it can take effect. Section 13(1) of the European Union (Withdrawal) Act 2018 ("2018 Act") provides that the Withdrawal Agreement with the EU may only be ratified under four conditions:

  • A copy of the relevant withdrawal documents must be laid before each House of Parliament (the required documents have now been laid);
  • The House of Commons must approve the Brexit deal;
  • The House of Lords must "take note" and debate the Brexit deal;
  • An Act of Parliament must be passed implementing the Brexit deal ("European Union (Withdrawal Agreement) Bill")

It is the Commons' decision currently scheduled for the 11 December2018 that is referred to as the "meaningful vote".

Can Parliament amend the terms of the Brexit deal?

The Commons' motion is a so called "substantive motion", which, under the House of Commons Procedure and Practice, is amendable. The Commons could therefore refuse a simple "yes motion" and instead offer conditional approval (e.g. approval on condition of second referendum), or approval subject to changes made to either the Withdrawal Agreement or the political declaration on the future relationship.

However, section 13 of the 2018 Act makes it clear that an absolute approval is needed in order for the Government to be able to ratify the Brexit deal.

Any amendments to the Government motion will not, though, alter the terms of the Brexit deal: that would remain a matter for the Government negotiating on behalf of the UK with the EU.

What happens if the Commons approves the Brexit deal on 11 December 2018?

If the Commons' approves the Brexit deal, the Government will be able to bring forward the European Union (Withdrawal Agreement) Bill in order to give it domestic legal effect. The Bill would be intended to implement the Brexit deal into UK law, ensure that the UK Government meet its international obligations, and provide further opportunity for parliamentary scrutiny.

Assuming the Bill is passed, the Brexit deal would then be expected to be laid before Parliament a second time: section 20 of the Constitutional Reform and Governance Act 2010 requires most international treaties (there are exceptions) to be laid before both Houses of Parliament for 21 sitting days prior to ratification. Once the treaty has been laid before Parliament and Parliament has not resolved against it, the Government may proceed with the ratification process.

Ratification establishes as a matter of international law the UK's consent to be bound by the terms of the Brexit deal. In the case of bilateral treaties, ratification usually takes the form of an exchange of the requisite instruments.

Once the Brexit deal has been ratified by the UK and concluded by the EU, and the Secretary General of the Council has received written confirmation (see section 185 of the Withdrawal Agreement), it will enter into force on 29 March 2019, 11 p.m. GMT ("exit day").

What if not?

One thing is certain: if the Commons refuses absolute approval on 11 December 2018, the Government won't be able to continue with ratifying the current Brexit deal with the EU. This potentially puts the UK on the path to a "hard Brexit" on exit day. The other domestic and international consequences are hard to predict.

Whether the UK would be able to unilaterally stop Brexit by withdrawing its Article 50 notice is currently being debated in the Court of Justice of the European Union in a case referred to it by the Court of Session in Edinburgh.