Was it legal for Boris Johnson to suspend parliament for five weeks before Brexit?
That's what Britain's Supreme Court will decide this week.
The Brexiteering prime minister asked the Queen to prorogue the house from last week to October 14.
Johnson argued the shutdown would give him time to introduce a new legislative agenda.
But his enraged critics accuse him of silencing lawmakers, and say the real reason was to prevent parliamentary scrutiny and challenges to his Brexit plans.
He no longer commands a majority in the House of Commons, where there is stiff opposition to his promise to leave the European Union by October 31st, even without a divorce deal.
Scotland's highest court ruled last week that the closure was unlawful.
But the week before, the high court of England and Wales ruled the opposite.
Both those cases are now before the Supreme Court, which will have the final say.
Since Johnson took the top job in July, Britain's Brexit crisis has gone into overdrive.
So what happens next if the court rules against him?
Anti-Brexit campaigners and lawmakers say parliament should be recalled immediately in that case.
And if judges decide he misled the queen, then he should resign.
Johnson was noncommittal this week, expressing his respect for the judiciary, but saying he'd wait and see what they said.
His Conservative government accuses Brexit's opponents of trying to use the courts to frustrate Brexit.
The Supreme Court has ruled against the government before on Brexit, back in 2017, when it ruled parliament would have approve the start of official talks with Brussels.
That case was led by Remain campaigner Gina Miller -- who is among those challenging the government this time round, along with former Conservative Prime Minister John Major.