A court comprising the Lord President, Lord Carloway, Lord Brodie and Lord Drummond Young ruled that Prime Minister Boris Johnson’s prorogation of Parliament was unlawful.

Elaine Motion, executive chairman of Balfour and Manson, the firm which instructed counsel for the petitioners, told SLN: “The effect of the Court of Session’s judgment today means that it is as if the prorogation order had never existed.

“The government did not ask the court to suspend its judgment this morning.

“Therefore, it is clear that Parliament can now reconvene and progress its work, including seeking the documents ordered of the government on Monday in relation to prorogation.”

In relation to an appeal, she added: “The Supreme Court will now determine this matter but in terms of its rules it can only suspend the judgment of a lower court in exceptional circumstances and simply failing to seek such an order from the lower court does not seem to qualify as ‘exceptional circumstances’.”

Stephen Tierney, professor of constitutional theory at Edinburgh Law School and legal adviser to the House of Lords Constitution Committee, described the judgment as “remarkable”.

He told SLN: “The Outer House’s refusal to grant interim orders was not entirely conclusive on the distinction between the decision by Her Majesty The Queen to prorogue and the advice upon which that decision was made.

“The necessary inference was that both dimensions of the decision were non-justiciable. The Inner House draws the distinction more sharply but its conclusions will have vital implications for both, declaring not only the advice given but the prorogation itself to be unlawful and hence ‘null and of no effect’.”

Professor Tierney suggested several aspects of the full judgment, to be released later this week, will be interesting, namely “how the court reasons its way to justiciability; to what extent its reading of the government’s motives was vital to establishing justiciability – something Lord Brodie seems to suggest; and, most interestingly of all, how the court navigates the relationship between the established grounds of judicial review on the one hand and broader constitutional principles on the other in arriving at its decision”.

He added: “The Lord President seems to take the view that advice to Her Majesty on the exercise of the royal prerogative of prorogation is not reviewable on normal judicial review grounds – something which many expected, given the high political significance of this prerogative power – but that the purpose for which this advice is given is reviewable through a different avenue, founded upon what is taken to be high constitutional principle.”

Professor Tierney said that while the decision’s “political salience will in the short term be greater than its legal resonance”, “the court’s reasoning on these crucial constitutional points and how they are received by the Supreme Court could have lasting implications for our constitution, for the reviewability of major prerogative powers and for the courts themselves if this marks a preparedness to intervene on matters of high constitutional principle to an extent rarely seen before”.

The Supreme Court will hear Brexit-related judicial review cases from Tuesday with a bench comprising the following 11 justices: Lady Hale, President of the Supreme Court; Lord Reed, Deputy President; Lord Kerr; Lord Wilson; Lord Carnwath; Lord Hodge Lady Black; Lord Lloyd-Jones, Lady Arden, Lord Kitchin and Lord Sales.