LONDON — Britain’s government warned lawmakers not to try to “thwart the will of the people” after the Supreme Court ruled Tuesday that Prime Minister Theresa May must seek the approval of Parliament before starting the formal process of leaving the European Union.
The 8-3 decision forces the government to put a bill before Parliament, giving members of the House of Commons and the unelected House of Lords the chance to debate and potentially offer amendments that could soften the terms of Britain’s exit from the EU, known as Brexit.
While the government insisted its timetable of starting the talks by the end of March remained on track, some analysts warned that a defeat in the House of Lords, where May does not have a majority, could delay the process by a year or more.
“Parliament will rightly scrutinize and debate this legislation,” David Davis, the government’s Brexit secretary, told the House of Commons after the ruling. “But I trust no one will seek to make it a vehicle for attempts to thwart the will of the people, or frustrate or delay the process of our exit from the European Union.”
While the ruling won’t scuttle Britain’s departure, mandated by voters in a June 23 referendum, it once again highlights the uncertainties in negotiating the country’s future relationship with the bloc of 500 million people, which is central to trade, immigration and security. The pound has fallen about 20 percent against the dollar since the vote on concern about slower economic growth and reduced investment.
Putting the issue before Parliament is not a simple matter. While May holds sway in the House of Commons, the House of Lords have in recent years stalled dozens of pieces of legislation with which they disagreed, including an attempt by May’s predecessor to impose welfare cuts on the vulnerable. The government backed down after the delay.
The lawsuit was considered the most important constitutional case in a generation because it centered on the question of who ultimately wields power in Britain’s system of government: the prime minister and her Cabinet, or Parliament.
May had said she would use centuries-old powers known as royal prerogative to invoke Article 50 of the EU treaty and launch two years of exit talks. The powers — traditionally held by the monarch — permit decisions about treaties and other specific issues to be made without a vote of Parliament.
The prime minister argued that the referendum gave her a mandate to take Britain out of the 28-nation bloc and that discussing the details of her strategy with Parliament would weaken the government’s negotiating position.
Financial entrepreneur Gina Miller sued to force the government to seek parliamentary approval. Leaving the EU, she said, would change the fundamental rights of citizens and this can’t be done without a vote of lawmakers. The Supreme Court agreed.
“The referendum is of great political significance, but the act of Parliament which established it did not say what should happen as a result, so any change in the law to give effect to the referendum must be made in the only way permitted by the U.K. constitution, namely by an act of Parliament,” Supreme Court President David Neuberger said in reading the decision.
“To proceed otherwise would be a breach of settled constitutional principles stretching back many centuries,” he said.
Significantly, the government did win one argument on Tuesday, with the ruling that the legislatures of the nations that are a part of the United Kingdom — Scotland, Wales and Northern Ireland — do not need to be consulted on Brexit. Such consultation would likely have led to a significant delay as lawmakers from the regions piled in with their concerns.