A legal challenge over Brexit is due to be heard at the European Court of Justice (ECJ).
A cross-party group of politicians launched the action to determine whether the UK can unilaterally revoke its Article 50 request to leave the European Union.
Those bringing the case believe the UK Parliament could halt the Brexit process if MPs vote down the final deal, while the UK Government argues the case is hypothetical as it has no plans to revoke Article 50.
A hearing is scheduled for Tuesday in Luxembourg in a bid to determine whether the withdrawal process triggered under Article 50 can be halted by the UK on its own, without prior consent of the other 27 EU member states.
The ECJ is the highest court in Europe regarding EU law.
The hearing was fixed after the highest court in the UK, the Supreme Court, last week rejected the UK Government’s application to appeal against the ruling made by Lord Carloway at the Court of Session in Edinburgh in September to refer the question to the ECJ.
The case was launched in February 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.
Under pressure, the Govt has finally published the text of its (failed) application for permission to appeal to the Supreme Court. What is significant is that the Govt formally recognises MPs can simply direct it to revoke the Article 50 notice. https://t.co/vCjTlvvlXVpic.twitter.com/iBpjCyU03M
— Jo Maugham QC (@JolyonMaugham) November 26, 2018
In June, Lord Boyd refused their request to refer the case to the ECJ, ruling the question was “hypothetical” and the conditions for a reference had not been met.
The September judgment of Lord Carloway, Scotland’s most senior judge, overturned this ruling.
He said the European court would not be advising the UK Parliament on “what it must or ought to do” but instead “merely declaring the law as part of its central function” and “how Parliament chooses to react to that declarator is entirely a matter for that institution”.
He added: “It seems neither academic nor premature to ask whether it is legally competent to revoke the notification and thus to remain in the EU.
“The matter is uncertain in that it is the subject of a dispute; as this litigation perhaps demonstrates.
“The answer will have the effect of clarifying the options open to MPs in the lead up to what is now an inevitable vote.”
No judgment is expected at Tuesday’s hearing and it is understood the European court will issue a written judgment later.
In its ruling, the Supreme Court stipulated the Court of Session will have to reach a judgment on the matter after the ECJ has given guidance.
Mr Wightman is among those travelling to Luxembourg and said he is “looking forward” to the hearing.
He added: “The question as to whether MPs can unilaterally revoke Article 50 is vital, as the chaos around Brexit shows no sign of being resolved.
“The UK Parliament must be fully informed of all of its options.”
A UK Government spokesman said: “It remains a firm matter of policy that we will not be revoking Article 50.”