The Court of Session has ruled today that the Prime Minister’s advice to the Queen to prorogue Parliament, and the prorogation that followed, was unlawful and so is null and of no effect. This is a startling – and misconceived – judgment. It does not though seem itself to recall Parliament into session, if that were even possible for a court to rule.

Only a summary of the Scottish Court’s reasoning has been released, with the full judgment to follow on Friday. Meanwhile the High Court in London has today released its reasons for rejecting Gina Miller and John Major’s legal challenge to prorogation. Its judgment is a powerful restatement of the orthodox legal view, and firmly and rightly rejects the constitutionally dubious argument that parliamentary sovereignty permits or requires the courts ‘to exercise hitherto unidentified power over the Executive branch of the state in its dealings with Parliament.’ The circumstances and reasons for proroguing Parliament are for the Government to decide.

The Government is bound by law in Scotland and Northern Ireland, just as much as in England and Wales, which is partly why litigation was commenced in all three places. It will now be for the Supreme Court, which hears an appeal on Tuesday, to decide whether the advice to prorogue Parliament is for the courts to decide and, if it is, whether Tuesday’s prorogation was unlawful.

The Scottish court at first instance had found that there were no legal standards that the Court could apply in this context. The High Court reached its decision on similar grounds, mainly because this is an obvious, legally unimpeachable line of reasoning. Why has the Court of Session taken a different view today?

The Court seems to have ruled that the Prime Minister’s advice to Her Majesty about prorogation was not reviewable on ordinary judicial review grounds, but on fundamental constitutional principles. Oddly, however, the Court seems to have reasoned that the Prime Minister acted for an ‘improper purpose’, which is an ordinary ground for judicial review. Perhaps this is an attempt to circumvent the rule that justiciability (the limits on which questions courts should decide) is determined before the grounds of review are considered, but it leaves the reasoning (or at least the Court’s summary of its reasoning) looking very confused.

In addition to seeming internally inconsistent, the Court’s ruling appears to be grounded in a novel elevation of very general constitutional principles into actionable propositions of law. So the Court’s summary refers to parliamentary scrutiny of the executive being ‘a central pillar of the good governance pillar enshrined in the constitution’. But there is no such free-standing pillar. What is the source of law for the claim that ‘good governance’ is legally actionable? The Court might answer that it stems from the principles of democracy and the rule of law. But the courts do not have free licence to uphold ‘democracy’ writ large and, save in special circumstances, they uphold the rule of law by applying settled law, not by departing from settled law in the name of some abstract principle.

The Court goes on to assert that this particular prorogation was: ‘a tactic to frustrate Parliament’ and was intended:

‘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’.

This is a bold inference about the Government’s intentions. It may have been instead that the Government intended to bring to an end an overly long session of Parliament and to take the opportunity to begin a new Queen’s Speech.

Of course, in shortening the available time for Parliament to meet, the Government may also have been attempting to make it less likely that legislation would be passed, in violation of normal constitutional principle and practice. The attempt was rightly controversial and the proper place for its merits to be determined, and any sanction applied, was first in the House of Commons and second in the country at large, in the form of a general election.

But even if part of the reason for the prorogation was to shorten the available time Parliament has to legislate to compel the Government to apply for an Article 50 extension, the gambit has already failed, and was perhaps always doomed. Clearly Parliament did not, and does not, need judicial intervention to protect it.

The rationale for the judgment is that by maximising parliamentary sitting time, or at least quashing a longer than usual prorogation, the Court vindicates democratic principle. This line of argument is politically contestable. It requires the Court to examine the legitimacy of the Government’s relationship with Parliament, which includes its use of the royal prerogative – something a court is not well-placed to evaluate.

And again, most importantly of all, the Court does not have authority simply to enforce its own view about what good government consists of. The Court needs an established principle of law for adjudication according to law to be possible. Its invocation of grand constitutional principle reads, in summary form at least, like an admission that there were no legal grounds on which to justify its decision.

Today’s decision by the Court of Session is a mistake. It forms part of a continuing, worrying trend for politically motivated litigation to secure some success in our courts, a trend which it is to be hoped the Supreme Court will bring to a halt.

Strikingly, the Court’s summary of its reasoning says nothing about the Northern Ireland (Executive Formation etc.) Act 2019, which Parliament enacted in late July and which addresses the question of prorogation in the Autumn. The Government acted within the strictures of that Act and it is very surprising that the Court has chosen to quash action which Parliament, as recently as July, chose to tolerate.

In the meantime, one wonders whether Parliament has just been returned, by judicial order, to session. It seems not. The Court of Session has made an Order ‘declaring’ that the advice to prorogue and the prorogation was unlawful and is thus null and of no effect. However, the Court seems not to have ordered any further actions, and appears to have left it to the Supreme Court to decide what happens next. The Court should really have been crystal clear on this point.

It bears noting also that Parliament has already been prorogued. Prorogation is a process that is carried out within the Houses of Parliament and which is subject to the overriding constitutional principle that proceedings in Parliament should not be called into question in any court. That is, the Government’s advice to the Queen may have been unlawful but the prorogation could remain legally effective. There is a good argument, in other words, that even if the Supreme Court upholds the Court of Session and overrules the Divisional Court, it may not have the authority to end Parliament’s prorogation.

The Government said, in the High Court, that it would abide by the Court’s judgment. This might mean that if the Supreme Court were next week to uphold the Court of Session, the Government would comply with the Supreme Court’s ruling by taking steps to shorten the prorogation or otherwise to have Parliament recalled to session. However, the Government may say instead that if the High Court had ruled the advice to prorogue unlawful it would not have proceeded with prorogation. This does not necessarily settle the question of what happens now that Parliament has been prorogued.

Richard Ekins is Head of Policy Exchange’s Judicial Power Project and Professor of Law, University of Oxford