A Scottish court is considering a legal attempt to block the suspension of the UK parliament.
Seventy five parliamentarians are seeking an interim interdict that would halt the move by the government.
They began legal action at the Court of Session in Edinburgh last month to prevent a Westminster shutdown.
They are now seeking the Scottish legal equivalent of an injunction to stop parliament being suspended, pending a full hearing on 6 September.
The Queen has already agreed to the prime minister’s request to suspend Parliament for five weeks on 10 September.
Boris Johnson has said the Queen’s Speech would then take place on 14 October, to outline his “very exciting agenda” of new legislation.
Critics, however, say that makes it unlikely MPs would have enough time to pass laws to stop a no-deal Brexit happening on 31 October.
Aidan O’Neill QC, representing the parliamentarians, told judge Lord Doherty: “Powers of the executive are never unlimited or unfettered.
“We do not live in a totalitarian state.”
Mr O’Neill said there had been a number of examples where an order already “signed off” by the Queen had been successfully challenged.
He went on to argue the suspension of parliament meant a denial of “political accountability” and was unconstitutional.
The QC said the case came before the court as matter of urgency in light of yesterday’s announcement.
He argued that a previous case, involving Telegraph owners the Barclay brothers, saw them successfully challenge the validity of Privy Council advice to the Queen.
Mr O’Neill cited a separate case where, he said, it showed there was an “obligation on the sovereign to recall an order of prorogation” if the court was satisfied there had been an “abuse of power”.
He said an action raised in the Scottish courts was as valid as one raised in any other UK court, giving the example of a Brexit-related court challenge in Northern Ireland.
After the QC quoted the Claim of Right from 1689 – which asserted the sovereignty of the old Scots parliament – Lord Doherty asked if there was a more recent precedent.
Mr O’Neill said there was none that matched the gravity of the present situation.
The legal challenge launched in the Scottish courts last month is being led by SNP MP Joanna Cherry and Liberal Democrat leader Jo Swinson, aided by Jo Maugham of the Good Law Project.
They want the court to rule that shutting down parliament – known as proroguing – ahead of Brexit would be “both unlawful and unconstitutional” and would have “irreversible legal, constitutional and practical implications for the United Kingdom”.
In a tweet Ms Cherry, who is also a QC, said: “Lord Doherty will hear legal arguments from both sides for around two hours.
“It’s possible he could then grant an interim interdict preventing the suspension of Parliament.
“The UK Gov legal team would immediately move to reclaim, ie appeal.”