https://www.instituteforgovernment.org.uk/explainers/court-challenges-prorogation
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Didn’t the English High Court already rule that the prorogation was lawful?
Yes. The English High Court ruled that, according to English and Welsh public law, the prorogation was lawful. The High Court said that the question of whether the government had left MPs sufficient time to hold the executive to account was a political question, which could not be decided by the court.
However, the Scottish Court of session
does not apply English and Welsh public law. It applies Scots public law, and was not bound by the decision of the High Court. The Scottish Court of Session ruled that, according to Scottish public law, the prorogation was unlawful."
Does the court’s ruling mean that Parliament is in session after all?
Because the summary of the court’s judgment says that the prorogation was “null and of no effect”, the challengers say that Parliament was never prorogued at all.
However, it appears that the court has only said that it “will” make such an order to that effect, and has not yet actually made the order. This may be because the Supreme Court is due to hear an appeal on Tuesday.
Therefore, it appears for now that Parliament is still prorogued.
However, the Court of Session
has said that the prorogation was unlawful even if it has not made the order. The government normally responds to legal judgments against it by taking steps to bring itself into compliance with the law. For that reason, the Labour Party has
called on the government to recall Parliament immediately. The government has reportedly
said that it will await the Supreme Court’s judgment."