LONDON — Dealing a blow to independence-minded Scots, the British Supreme Court ruled on Wednesday that the Scottish Parliament could not unilaterally schedule a second referendum on whether to break away from the United Kingdom.
In a unanimous ruling, the court said that the decision on whether to hold a referendum could not be made without the consent of the British Parliament. Britain’s government has consistently rejected calls by the Scottish National Party for another referendum, after a previous such vote fell short in 2014.
“A lawfully held referendum would have important political consequences relating to the Union and the United Kingdom Parliament,” Robert Reed, the Supreme Court’s president, said in reading the decision. As a result, he added, legislation to hold a vote was a matter “reserved” for the Parliament in London.
The court rejected an argument by Scottish nationalists that they should be allowed to hold a referendum on the basis of their right to self-determination under international law. The Scots, it said, did not meet the threshold of being an “oppressed” people who would warrant such status.
The widely expected decision lifted one of the clouds hanging over the British prime minister, Rishi Sunak. He is struggling with an economic crisis, a fraught relationship with the European Union, and division in his Conservative Party after political upheavals toppled two of his predecessors in the past four months.
But the setback for those advocating Scotland’s separation is unlikely to stop the independence movement, which has gained momentum since Britain voted to leave the European Union in 2016. Scotland’s first minister, Nicola Sturgeon, said that the ruling underscored the need for Edinburgh to break free of being ruled from London.
“Scottish democracy will not be denied,” Ms. Sturgeon posted on Twitter. “Today’s ruling blocks one route to Scotland’s voice being heard on independence — but in a democracy our voice cannot and will not be silenced.”
Still, as a practical matter, the ruling is a hurdle. A referendum held without Britain’s approval would lack international legitimacy, which could complicate Scotland’s professed goal of rejoining the European Union as an independent nation. In the 2016 Brexit referendum, Scots voted to remain part of the bloc.
The Scottish Parliament had hoped to schedule a second independence referendum for next October, giving it time to mobilize support. In 2014, Scots voted against leaving by 55 percent to 45 percent. Support has waxed and waned since then, but polling since Brexit has often shown increased support for separating.
In a survey of public attitudes released in September, the nonprofit National Center for Social Research found that 52 percent of people in Scotland supported independence, up from 23 percent in 2012. “The Union has certainly become decidedly less popular north of the border,” the survey’s authors wrote.
Mr. Sunak, who became prime minister last month, is less unpopular in Scotland than previous British leaders, particularly his former boss, Boris Johnson. In August 2020, Mr. Johnson sent Mr. Sunak, then the chancellor of the Exchequer, to Scotland to try to tamp down nationalist sentiment.
But now, Mr. Sunak faces other headwinds. Public sentiment has swung against Brexit as Britain’s economy has deteriorated. That could feed the desire of Scots to break away, given that Brexit was never popular there. After the Supreme Court ruling on Wednesday, the British government, welcoming the decision, tried to change the subject.
“People in Scotland want both their governments to be concentrating all attention and resources on the issues that matter most to them,” the Scotland secretary, Alister Jack, said in a statement. “That’s why we are focused on issues like restoring economic stability, getting people the help they need with their energy bills, and supporting our N.H.S.”