The Attorney General and the Advocate General are expected to lodge a formal application over the legality of the Continuity Bill at the Supreme Court on Monday or Tuesday.
The legislation, which is designed to plug any gaps in Scottish laws on the day of Brexit, was passed by MSPs at the Scottish Parliament last month as talks between the two governments stalled.
Ministers pushed ahead with the Bill against the advice of Presiding Officer Ken Macintosh, who said he believed the Bill was outside Holyrood’s remit after taking legal advice.
It is the first time that the Scottish Government has proceeded with a Bill against the advice of the PO, and government legislation being directly referred to the Supreme Court is also unprecedented.
The Bill has been backed by Scotland’s Lord Advocate, James Wolffe QC, who told MSPs it had been specifically worded to avoid altering or undermining EU law while the UK was still a member.
Earlier this week Scottish Secretary David Mundell said it was “almost inevitable” that the Bill would have to be tested by the Supreme Court due to its unprecedented nature.
“When you have that degree of uncertainty, then you know inevitably it needs to be clarified. I don’t regard it as a big deal as such. That’s where the process takes you,” he told the Press and Journal.
The UK’s top legal officials only have 28 days to lodge a legal challenge to a Scottish Government Bill after it is passed by MSPs, meaning they must act by the end of Wednesday.
It is understood that on the day the formal court application is lodged, UK ministers will argue that they are merely following due process rather actively seeking to stop Scotland making its own laws.
The legal challenge is also expected to include Wales, where Assembly Members passed their own version of the Continuity Bill on the same day as Holyrood.
The Bill mimics the functions of the UK Government’s EU Withdrawal Bill, which has been described by Nicola Sturgeon and Carwyn Jones as a “power grab” that will undermine devolution.
Talks with the devolved nations on that Bill remain deadlocked after months of negotiations, with the UK insisting it should retain control of 24 devolved areas after Brexit.
Ministers argue this would only be a temporary measure to avoid the risk of harming trade within the UK, but the Scottish Government wants the powers to go straight to Holyrood.
The Continuity Bill is supposed to act as a backstop in case no agreement is reached and the Scottish Parliament refuses to give its consent to the passage of the Withdrawal Bill.
A spokeswoman for the Attorney General said the UK’s law officers were currently “considering the position” on the Continuity Bills.
A spokeswoman for the Supreme Court said it was unable to comment on “hypotheticals”, but that an announcement would be made as soon as possible after any application was received.
A Scottish Government spokesman said: “The Continuity Bill was passed overwhelmingly by the Scottish Parliament. Scottish Ministers are satisfied that the Bill is within legislative competence.”
This article originally featured on our sister website inews.co.uk.