– The British government and its opponents faced off Tuesday at the U.K. Supreme Court in a high-stakes legal drama over Brexit that will determine whether new Prime Minister Boris Johnson broke the law by suspending Parliament at a crucial time ahead of Britain's impending departure from the European Union.

As pro-E.U. and pro-Brexit protesters exchanged shouts outside the court building on London's Parliament Square, the government's opponents argued that Johnson illegally shut down Parliament just weeks before the country is due to leave the 28-nation bloc for the "improper purpose" of dodging lawmakers' scrutiny of his Brexit plans. They also accused Johnson of misleading Queen Elizabeth, whose formal approval was needed to suspend the legislature.

The government countered that, under Britain's largely unwritten constitution, the suspension was a matter for politicians, not the courts.

Government lawyer Richard Keen said judges in a lower court had "nakedly entered the political arena" by ruling on the matter. "The court is not equipped to decide what is a legitimate political consideration," he said.

Johnson sent lawmakers home on Sept. 9 until Oct. 14, which is barely two weeks before the scheduled Oct. 31 Brexit day. A ruling against the government by the country's top court could force him to recall Parliament.

Johnson hasn't said what he would do if the judges rule the suspension illegal. He told the BBC on Monday he would "wait and see what they say."

Keen promised that "the prime minister will take any necessary steps to comply with any declaration made by the court." But he had no answer when judges asked if Johnson might recall Parliament on the court's order, only to suspend it again.

"I'm not in a position to comment on that," he said.

The prime minister says Britain must leave the E.U. at the end of next month with or without a divorce deal. But many U.K. lawmakers believe a no-deal Brexit would be economically devastating and socially destabilizing, and they are determined to thwart him.

Lawyer David Pannick, who represents one of the campaigners challenging the government, told 11 Supreme Court judges that Johnson had improperly suspended the legislature "to silence Parliament … because he sees Parliament as an obstacle to the furtherance of his political aims."

Johnson says the suspension is routine and will allow his government to launch its domestic agenda with a new session of Parliament. But the decision outraged many lawmakers, who say it's designed to prevent them from challenging Johnson's push for Brexit in October "do or die."

The suspension sparked legal challenges, to which lower courts have given contradictory rulings. England's high court said the move was a political rather than legal matter, but Scottish court judges ruled last week that Johnson acted illegally "to avoid democratic scrutiny."

The Supreme Court is being asked to decide who was right, in a case scheduled to last up to three days. It is considering two questions: Is this a matter for the courts; and, if so, did the government break the law?

The government denies misconduct, arguing in a written submission that the issue is "intrinsically one of high policy and politics, not law."

Keen, acting for the government, told the court that the Scottish judges "have simply gone where the court should not go." He insisted there was nothing improper in the government's behavior.