Brexit legislation passed by the Scottish Parliament will be scrutinised at the UK's highest court.
Supreme Court justices in London are being asked to rule on whether Holyrood's EU exit bill is constitutional and "properly within devolved legislative powers".
The move seeking "legal certainty" over the legislation was taken "in the public interest" by the attorney general and the advocate general for Scotland.
A panel of seven justices, including the court's president Lady Hale and deputy president Lord Reed, will hear argument over two days, beginning on Tuesday.
The issue the judges are being asked to decide is whether the bill "is within the competence of the Scottish Parliament".
When details of the case were announced in April, the then Attorney General Jeremy Wright said: "This legislation risks creating serious legal uncertainty for individuals and businesses as we leave the EU.
"This reference is a protective measure which we are taking in the public interest."
Advocate general for Scotland Lord Keen said: "By referring the Scottish Parliament's Continuity Bill to the Supreme Court we are seeking legal certainty as to its competence."
The Scottish Parliament's presiding officer previously ruled the Scottish EU Continuity Bill is outside Holyrood's competence - although SNP ministers say they are confident it is not.