The U.K.’s Court of Session, the highest court in Scotland, has ruled that Boris Johnson’s advice to the Queen to prorogue Parliament and the prorogation itself were unlawful. Here are the conclusions from the ruling:

It was incumbent on the UK Government to show a valid reason for the prorogation, having regard to the fundamental constitutional importance of parliamentary scrutiny of executive action. The circumstances, particularly the length of the prorogation, showed that the purpose was to prevent such scrutiny. The documents provided showed no other explanation for this. The only inference that could be drawn was that the UK Government and the Prime Minister wished to restrict Parliament.

The Court also decided that it should not require disclosure of the unredacted versions of the documents lodged by the respondent.

The Court will accordingly make an Order declaring that the Prime Minister’s advice to HM the Queen and the prorogation which followed thereon was unlawful and is thus null and of no effect.

This is the latest in a series of defeats for Johnson since he became prime minister, and it could make things extremely difficult for him in the coming months if this ruling is upheld. Johnson has already set a record for the number of parliamentary defeats he has suffered in the last two weeks, and this ruling could be one of the most significant blows to his government. David Allen Green of The Financial Times notes that the ruling also found that the prime minister has misled the Queen in order to get her to agree to the prorogation:

Senior Scottish judges on Wednesday held unanimously that the prorogation of the UK parliament was unlawful, and they did so on the basis that prime minister Boris Johnson misled the Queen. This is a remarkable and unprecedented judgment, and it is of profound importance, even though there will be an appeal hearing next week.

Because it was a Scottish court, it was able to judge the matter under Scots law, which gave the judges more leeway in assessing the government’s reasons for seeking the prorogation. That allowed them to decide that Johnson had knowingly sought it under false pretenses:

In effect, though not in express terms, the Scottish court has held that Mr Johnson lied to the Queen. Not only was the advice false, but it was known by the prime minister to be false. Mr Johnson acted in bad faith.

That finding is a damning indictment of Johnson, and as Green observes it is also the first time that a prime minister has been found to have done this:

But this defeat is of far more constitutional significance than that of any vote in the House of Commons. He is the first UK prime minister to have been found by a court to have misled the sovereign.

Following the ruling, there have been calls from many lawmakers to recall Parliament, and depending on next week’s ruling that may very well happen. James Forsyth explains what this will likely mean in practice:

If parliament does end up returning early, it would make life very difficult for Boris Johnson. It has, of course, already passed legislation requiring the Prime Minister to seek an extension if no deal has been reached by October 19th. But convinced of its own righteousness, it would use this extra time to go on various fishing expeditions—demanding the messages of various aides and more no deal planning documents. Rather than being able to use the Prime Ministerial bully pulpit to command the news agenda, Boris Johnson would find himself being defeated in parliament on an almost daily basis.