Campaigners have won their High Court battle over Theresa May’s decision to use the royal prerogative in her Brexit strategy.
In one of the most important constitutional cases in generations, three senior judges ruled the Prime Minister does not have power to use the prerogative to trigger Article 50 of the Lisbon Treaty to start the UK’s exit from the European Union – without the prior authority of Parliament.
The ruling against the Government was made by Lord Chief Justice Lord Thomas, sitting with two other senior judges in London.
Unless overturned on appeal at the Supreme Court, the ruling threatens to plunge the Government’s plans for Brexit into disarray as the process will have to be subject to full parliamentary control.
Government lawyers had argued that prerogative powers were a legitimate way to give effect “to the will of the people” who voted by a clear majority to leave the European Union in the June referendum.
But the Lord Chief Justice declared: “The Government does not have power under the Crown’s prerogative to give notice pursuant to Article 50 for the UK to withdraw from the European Union.”
The Government has been given the go-ahead to appeal against the ruling at the Supreme Court but made no immediate announcement about whether it will.