Will Brexit happen on 31 October?

It is far from certain that Boris Johnson will be able to deliver on his promise to bring the UK out of the EU on 31 October “no ifs, no buts”. But as we explain, there are some relative legal certainties amid all the confusion.

The Government has been given a strong reminder of the limits of executive power

The Supreme Court ruled on 24 September that the Government’s prorogation of Parliament was unlawful and ineffective. Although the Supreme Court emphasised that its judgment was not about Brexit, it would be surprising if its ruling did not have an effect on the Brexit strategy the Government is pursuing.

The Supreme Court was not concerned with Prime Minister Boris Johnson’s motives for advising the Queen to exercise her prerogative powers to shut down Parliament for five weeks. Instead its ruling focused on the fact that in the current exceptional circumstances, such an unprecedentedly long prorogation would have the effect of “frustrating or preventing, without reasonable justification” the ability of Parliament to carry out its core constitutional functions, not only as the legislature but also as the body responsible for supervision of the executive.

In the court’s view, no reasonable justification had been given. It therefore declared that the resulting prorogation of Parliament had been a nullity and Parliament has now resumed sitting.

The Prime Minister is legally required to seek an extension in the absence of a deal

Shortly before MPs left Parliament for what has now turned out to be an unlawful and ineffective prorogation, the European Union (Withdrawal) (No 2) Act took effect. This Act was passed in record time with the support of a coalition of opposition parties to attempt to ensure that the UK does not leave the EU without a deal on 31 October.

The Act does not make a no-deal Brexit impossible, since the EU has to agree to any extension of the Brexit deadline. But it does make it much less likely, since it requires the Prime Minister to seek an extension until 31 January 2020 if, by 19 October, an exit deal has not been reached with the EU and approved by Parliament (assuming Parliament has not by then voted in favour of leaving without a deal).

Some have argued that this legislation is flawed. Certainly it assumes that we have a working Government when the deadline is reached. However, while there has been speculation about whether and how Mr Johnson will comply with the letter of this legislation, it seems likely that the extension request will be made, either by the Prime Minister or through other compliance mechanisms which opposition MPs are exploring, involving either Parliament or the courts.

A deal on a withdrawal agreement remains possible

19 October is the crucial date in the EU Withdrawal (No 2) Act, since it is immediately after the next EU Council summit, which is due to take place on 17-18 October. If a deal is not reached then, it is still possible that efforts to secure a deal will continue right up to the 31 October deadline, even if an extension has been agreed in principle before that date.

It is clear that both sides would prefer a deal if this is at all possible, but the current EU position and Parliamentary arithmetic makes it look difficult to secure one that is acceptable to both the EU and the current Government, and which will also secure a majority in the House of Commons.

At the time of writing the Prime Minister has just delivered a brief outline of his Government’s revised proposals for a new deal to the Conservative Party Conference, but the full details of these proposals, and the EU’s likely response, remain unclear.

There is a basic legal framework in the UK for no deal, but a lot of gaps remain

It is worth reminding ourselves that the Government has thought through a high level strategy for plugging the gaps in our legal system once we leave the EU. The EU Withdrawal Act 2018 provides the necessary framework, which is based on importing into domestic law the vast majority of EU law that currently applies directly in the UK because of its EU membership. The Government is also well on the way to completing the necessary adjustments to our existing EU-derived law via hundreds of statutory instruments, which will take effect on 31 October in the absence of a ratified deal or an extension.

However, the UK will need to develop its own law in a number of key areas – for example to deal with future immigration from the EU or to create a new regime to replace EU agricultural subsidies and research grants. For now, the current Government’s strategy is broadly to preserve the status quo, as far as unilateral action can achieve that.

Hope for the best, prepare for the worst

On the surface at least, we have not moved forward from the unsatisfactory position that UK residents and organisations were in six months ago, in the run up to the original 31 March deadline. It follows that previous no-deal preparations will need to be revisited, without knowing for sure that they will actually be required.

But perhaps we are a little nearer to a resolution of this crisis. The main opposition parties now have clearer strategies for dealing with Brexit in the event that we have not already left the EU by the next general election. Labour, although divided, will support a second referendum with remain as an option, while the Lib Dems have committed to revoking Article 50 if they form the next Government. It seems likely that the Conservatives will position themselves as a pro-Brexit party, but one would assume that they would like to have at least the bare bones of a future deal to put to the country in a bid to be returned with a working majority.

Further reading

  • We have refreshed our key no-deal briefings on our Brexit hub.
  • The Government’s growing collection of no-deal guidance notes can be found here.
  • The corresponding EU preparedness notices can be accessed here.


Our content explained

Every piece of content we create is correct on the date it’s published but please don’t rely on it as legal advice. If you’d like to speak to us about your own legal requirements, please contact one of our expert lawyers.

Mills & Reeve Sites navigation
A tabbed collection of Mills & Reeve sites.
My Mills & Reeve navigation
Subscribe to, or manage your My Mills & Reeve account.
My M&R


Register for My M&R to stay up-to-date with legal news and events, create brochures and bookmark pages.

Existing clients

Log in to your client extranet for free matter information, know-how and documents.


Mills & Reeve system for employees.