Boris Johnson's decision to suspend the British parliament later this month until mid-October is lawful, a judge in Scotland has ruled.
A group of 70 MPs had been seeking to have a court in Edinburgh issue an injunction blocking the move.
However, that bid has now been rejected by a judge at the Court of Session.
Those behind the legal bid pledged to immediately appeal the decision.
In a tweet, SNP MP Joanna Cherry said: "Judge rules court can’t review exercise of prerogative power to prorogue. We thinks he’s erred in law on this point & others & will seek to appeal immediately."
Lawyers involved in the bid say they hope an appeals court will hear the case this week, and a potential Supreme Court hearing later in the month.
The Scottish case is one of three challenges to Boris Johnson's plan to prorogue parliament, with other cases underway in London and Belfast.
The English challenge was launched by campaigner Gina Miller, and the likes of former prime minister John Major and Labour deputy leader Tom Watson have since joined the bid.
Boris Johnson has insisted the suspension of parliament is to allow him to put forward his new government's legislative agenda through a traditional Queen's Speech.
Opponents of the move, meanwhile, claim it's an attempt to limit MPs' time to block a no-deal Brexit ahead of the October 31st deadline.