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-EU 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 II, 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 will 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.