The High Court in London ruled Thursday that the British government alone cannot start the process of leaving the European Union but requires the approval of parliament, in a landmark judgment that could delay Brexit.
Three senior judges said Prime Minister Theresa May's government does not have the power itself to trigger Article 50 of the EU's Lisbon treaty, the formal notification of Britain's intention to leave the bloc.
"We hold that the Secretary of State does not have power under the Crown's prerogative to give notice pursuant to Article 50 for the United Kingdom to withdraw from the European Union," the judgement said.
May's Downing Street office said it was "disappointed" at the decision and would appeal, with the case now expected to be heard in the Supreme Court in early December.
"The country voted to leave the European Union in a referendum approved by Act of Parliament," a spokesman said.
"Will (PM) finally give in to the temptation of calling an early election?" asks @bbclaurak #brexit #bbcdp https://t.co/A4eY4b2mfG — DailySunday Politics (@daily_politics) November 3, 2016
May previously accused those behind the legal challenge of seeking to frustrate the Brexit process, saying, "they're trying to kill it by delaying it."
But the claimants, including an investment fund manager, a hairdresser and an expatriate living in France, argue that Britain was taken into the EU by parliament, and only parliament can made the decision to leave.
"I am grateful to the court for the result, this is a victory for parliamentary democracy," expat Grahame Pigney told reporters outside court.
Sterling soars after UK court gives Parliament power to block #Brexit https://t.co/iTLWyNT6v6pic.twitter.com/cpUMYfJkzP — RT (@RT_com) November 3, 2016
"I now fear that every attempt will be made to block or delay the triggering of Article 50. If this is so, they have no idea of the level of public anger they will provoke."
During three days of hearings in October, May conceded that parliament would likely have a vote on the final deal negotiated with the bloc.
The case was heard by England's two top judges - Lord Chief Justice John Thomas and Master of the Rolls Terence Etherton and Philip Sales, an appeal court judge.
The court ruled that the government could not trigger Article 50 without approval from parliament.
"The court does not accept the argument put forward by the government," Thomas said. "We decide that the government does not have power to give notice pursuant to Article 50 for the UK to withdraw from the European Union."
The judges granted the government permission to appeal to the Supreme Court, Britain's highest judicial body, which has set aside December 5-8 to deal with the matter.
Investment manager Gina Miller, the lead claimant in the legal challenge, said the case was about "process, not politics" and rejected accusations of trying to usurp the will of the people.[caption id="attachment_28320" align="aligncenter" width="800"] Gina Miller, co-founder of investment fund SCM Private and the lead claimant in the case, reads a statement outside the High Court in central London on November 3, 2016 AFP[/caption]
"One of the big arguments (in the referendum) was parliamentary sovereignty," she told reporters. "So you can't on the day you get back sovereignty decide you're going to sidestep or throw it away."
Lawmakers largely voted to remain in the EU in the June referendum. Many investors believe greater parliamentary involvement in the process would therefore reduce the influence of ministers in May's government who are strongly pro-Brexit.
This could reduce the likelihood of a "hard Brexit", a scenario in which Britain prioritises tight controls on immigration over remaining in the European single market.
Nigel Farage, head of the anti-EU party UKIP, said on Twitter that he feared the ruling could turn into an attempt to scupper Brexit altogether.
"I worry that a betrayal may be near at hand," he said. "I now fear every attempt will be made to block or delay triggering Article 50. They have no idea (of the) level of public anger they will provoke."
I want to be absolutely clear. There will be no unnecessary delays in invoking Article 50. pic.twitter.com/xSmfzhiGTn— Theresa May (@theresa_may) October 2, 2016