A panel of three judges in the Court of Session, Scotland’s highest civil court, found that the decision to send lawmakers home for five weeks at the height of the Brexit crisis was “unlawful because it had the purpose of stymying Parliament.”

The ruling suggested that Mr. Johnson had misled Queen Elizabeth II, professing to want to shutter Parliament for banal procedural reasons while in fact asking her to do so to silence recalcitrant lawmakers opposed to his Brexit plans. It was another indication to some scholars of the prime minister’s open disdain for constitutional norms and legal obligations during the chaotic early weeks of his leadership.

It also deepened the political morass in which Mr. Johnson finds himself. In angling to extract Britain from the European Union by Oct. 31, with or without a deal, Mr. Johnson has lost his working majority in Parliament, exiled veteran Conservative lawmakers and failed twice to secure an early election. He is now promising to press ahead despite a law designed to stop a no-deal Brexit.

At least one ex-Conservative lawmaker said on Wednesday that the prime minister should resign if he lied to the queen. A few other lawmakers vowed to stage a sit-in to reopen Parliament.

The government had said it was suspending, or “proroguing,” Parliament to prepare for the start of a new legislative session. But the Scottish court disagreed, saying there was no evidence of Mr. Johnson doing anything but trying to free himself of parliamentary oversight as he pursued an abrupt Brexit over the objection of lawmakers.

“This was an egregious case of a clear failure to comply with generally accepted standards of behavior of public authorities,” a summary of the ruling said. “It was to be inferred that the principal reasons for the prorogation were to prevent or impede Parliament holding the executive to account and legislating with regard to Brexit, and to allow the executive to pursue a policy of a no-deal Brexit without further parliamentary interference.”

But the decision did not itself reopen Parliament. Instead it set up a showdown next week at Britain’s Supreme Court, which had already said it would review the case and take up the question of whether to halt the suspension of Parliament. [...]

Full article on The New York Times