Patrick Brown, managing partner at Tughans, gives an update on the legal challenges to Brexit.

Less than a week after the High Court in Belfast dismissed a legal challenge to the Prime Minister’s ability to trigger Article 50 using prerogative powers, the High Court in London has reached the opposite conclusion. The English High Court has supported the challenge led by Gina Miller, a London-based investment manager, and has ruled that the Government cannot trigger Article 50 on its own. Instead, Parliament must vote on whether the UK can start the process of leaving the European Union.

The Divisional Court, made up of the Lord Chief Justice, the Master of the Rolls, and Lord Justice Sales, stressed that its ruling was made purely on a point of law regarding the Crown’s prerogative powersand was nothing to do with the political decision to withdraw from the EU. Contrary to the Northern Ireland decision, the English judges decided that the giving of notice under Article 50 could not be separated from actual withdrawal since it was the notice which starts a process that will necessarily, not probably, lead to a change in domestic legislation. But the core finding of the court was that the European Communities Act 1972, which gives full effect to EU law in national courts, had displaced and removed the prerogative power of the Crown to “switch off the direct effect of EU law in the national legal systems of the UK”. In other words, only Parliament can make that decision.

It was not made clear what form a vote from Parliament should take and this could range from a one off substantive vote among MPs in the House of Commons to an entirely new, and no doubt complex, piece of legislation which would have to pass through both the House of Commons and the House of Lords. It is the latter option which the claimants in the English proceedings have been pushing for and either way, Northern Irish MPs will have a say in matters.

The Prime Minister has previously stated that she will trigger Article 50 by the end of March 2017. However, passing a new Act of Parliament would prolong the process. MPs may seek to amend and introduce various conditions into any proposed legislation, such as conditions regarding the negotiations around leaving the EU, meaning any proposed bill could take months, if not years, to agree.

Whether it be on foot of the decision in the Northern Irish or English Brexit challenge, it is inevitable that the issues around invoking Article 50 will be determined by the Supreme Court. The Government has been granted leave to appeal the decision made by the English High Court today and a spokesperson has since announced that it will do so. A Supreme Court hearing on the matter is expected to take place before the end of the year.