Lawyers for the group challenging the prorogation said there is "strong evidence" Johnson saw members of Parliament "as an obstacle" to Britain's departure from the European Union, and wanted to "silence" them.
Some lawmakers opposed the move to suspend so close to the Oct. 31 deadline. The Inner House of the Court of Session in Edinburgh previously ruled Johnson's decision was unlawful and "motivated by the improper purpose of stymieing parliament." Judges dismissed the case as "purely political" and "not a matter for the courts."
The Supreme Court will have a panel of 11 justices as it tries to sort through the various judgments. Tuesday marks just the second time 11 justices will sit in on one case.
Supreme Court President Lady Hale said the case would have no effect on the timing of the EU exit or "when and how" Britain leaves.
Johnson has insisted he had the authority to end the last session of Parliament until Queen Elizabeth II's speech on Oct. 14. That's also when his new government will outline a legislative plan for the year.
Johnson said he has "the greatest respect for the judiciary."
"And I think the best thing I can say, having said that, is to wait and see what they say," he said.