The Supreme Court rejected an application to appeal against a ruling to ask the European Court if the UK can unilaterally revoke its Article 50 request to leave the European Union.
The Court of Session in Edinburgh ruled in September to refer the question to the Court of Justice of the EU (CJEU) after a case brought by a cross-party group of politicians.
The CJEU applied its expedited procedure, as requested by the Court of Session, to the case and an oral hearing is fixed for November 27.
The UK Government made an application for permission to appeal against the ruling to the Supreme Court, which was refused by Lord Carloway, Scotland’s most senior judge and Lord President of the Court of Session in Edinburgh, earlier this month.
The Secretary of State for Exiting the European Union then applied directly to the Supreme Court for permission to appeal.
But, refusing permission on Tuesday, the court said the Court of Session’s ruling was “preliminary” and it would still have to reach a judgment on the matter after the European Court has given guidance.
A statement issued by the Supreme Court said: “It is clear that this interlocutor did not constitute a final judgment.”
It continued: “As both this court and the CJEU have made clear, the preliminary ruling is merely a step in the proceedings pending before the national court - it is that court which must assume responsibility for the subsequent judicial decision.
“It will therefore remain for the Court of Session to give judgment in the light of the preliminary ruling, any relevant facts which it may find and any relevant rules of domestic law. It is only then that there will be a final judgment in the proceedings.”
The initial case had been brought by a cross-party group of politicians: Labour MEPs Catherine Stihler and David Martin, Joanna Cherry MP and Alyn Smith MSP of the SNP, and Green MSPs Andy Wightman and Ross Greer, together with lawyer Jolyon Maugham QC, director of the Good Law Project.
The decision from Lord Carloway in September overturned an earlier ruling when it was said the question being asked was “hypothetical” and the conditions for a reference had not been met.
But Lord Carloway said it was “clear” MPs at Westminster would be required to vote on any Brexit deal agreed by the EU and the UK Government.
In his September judgment, Lord Carloway was clear the CJEU would not be advising Parliament on “what it must or ought to do”.
Instead, he said it would be “merely declaring the law as part of its central function”, adding that “how Parliament chooses to react to that declarator is entirely a matter for that institution”.