Ms May was going to invoke the “royal prerogative” (executive privilege) to initiate Brexit in March without the approval of Parliament.
The Prime Minister has now lost control of the entire Brexit process. The Court ruled that it is not up to ‘her’ - it is up to Parliament!
**Analysis - BBC political correspondent Eleanor Garnier
It is one of the most important constitutional court cases in generations. And the result creates a nightmare scenario for the government.
Theresa May had said she wanted to start Brexit talks before the end of March next year but this ruling has thrown the prime minister’s timetable up in the air.
Campaigners who brought the case insist it was about “process not politics”, but behind the doors of No 10 there will now be serious head-scratching about what the government’s next steps should be.
This decision has huge implications, not just on the timing of Brexit but on the terms of Brexit. That’s because it’s given the initiative to those on the Remain side in the House of Commons who, it’s now likely, will argue Article 50 can only be triggered when Parliament is ready and that could mean when they’re happy with the terms of any future deal.
Of course, it will be immensely difficult to satisfy and get agreement from all those MPs who voted to remain. Could an early general election be on the cards after all?**
**British court delivers blow to E.U. exit plan, insists Parliament has a say
Most members of Parliament opposed Brexit in the lead-up to Britain’s June referendum, when voters opted for an exit by a 52-to-48 margin. On the streets, however, the court decision risked setting off an angry backlash from voters who favored leaving the European Union and believed the issue was settled.
May’s lawyers argued that she had the right to begin the Brexit process without first getting Parliament’s consent. But a three-judge panel on the London-based High Court sided with a group of plaintiffs who contended that Parliament must first weigh in.
“The most fundamental rule of the U.K.’s constitution is that Parliament is sovereign and can make and unmake any law it chooses,” the judges wrote. “As an aspect of the sovereignty of Parliament it has been established for hundreds of years that the Crown – i.e. the Government of the day – cannot by exercise of prerogative powers override legislation enacted by Parliament.”
May will now have to decide whether to appeal to the Supreme Court. If she does, the proceedings could extend well into next year.
The court’s decision stunned British political and legal observers — just as the referendum outcome also defied the predictions that voters would favor staying in the E.U. family. Until Thursday, most analysts believed the court would side with the government.
It sparked an immediate rally in Britain’s beleaguered currency, the pound, as traders reacted to the possibility that Britain’s E.U. exit could be significantly delayed — or even blocked.
The pound has been battered since the referendum, and has been one of the worst performing currencies anywhere in the world this year. London’s FTSE exchange remained down slightly despite the announcement, but other markets, including France’s CAC, were higher in midday trading.
Pro-Brexit advocates quickly denounced the decision, saying it amounted to a betrayal of the public’s will.
“I now fear every attempt will be made to block or delay triggering Article 50,” tweeted Nigel Farage, a longtime Brexit champion. “They have no idea level of public anger they will provoke.”
Pro-E.U. politicians, meanwhile, celebrated the decision and called on May to share with Parliament her negotiating strategy — something she has steadfastly refused to do.