20 July 2016

In the first legal challenge to Brexit, four separate groups of claimants are arguing that only Parliament can invoke Article 50 of the Lisbon Treaty – the trigger for negotiations that will take the UK out of the EU – and are seeking a declaration that any attempt to invoke Article 50 through other means would be ultra vires. The government's lawyers, who confirmed to the Court that Article 50 is unlikely to be invoked before 2017, maintain that the decision to invoke Article 50 can be made by the Prime Minister under Royal Prerogative powers.

The four claims will be dealt with together, and the Court has indicated that the trial will take place on or around 15 October 2016. Given time constraints, we would expect judgment to be handed down very shortly after trial.

These proceedings are of such national and constitutional significance that, if the first instance decision is appealed, the Court has indicated that such an appeal may 'leapfrog' over the Court of Appeal and be heard directly by the Supreme Court. “Leapfrogging” is provided for in the Administration of Justice Act 1969, and applies where, amongst other things, there is a point of law of general importance in issue. “Leapfrogging” can mean that significant matters are resolved faster by the Court, but any dissenting views may result in further hearings. Given the government’s stated timetable for triggering Article 50, it may therefore be that any appeal in these proceedings will be heard before the end of the Court year – 21 December 2016.

These proceedings have already shed some light on the government's intentions and timetable for Brexit, and will no doubt continue to do so. For those involved in Brexit contingency planning, they will be an important source of information as to what is on the horizon as the impact of the June Referendum unfolds, and we will be monitoring developments on this website. Definitely one to watch.


Key contact

David Hall

David Hall Partner

  • Dispute Resolution
  • Banking Disputes
  • Business Crime and Regulatory Investigations

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