The court is hearing whether Brexit legislation passed by MSPs should be allowed to stand.

The Advocate General, Lord Keen of Elie QC, said the bill would undermine Westminster’s own EU Withdrawal Bill.

However, the Lord Advocate, James Wolffe QC, argued it is within Holyrood’s powers and should be law.

The European Union (Legal Continuity) (Scotland) Bill, which was opposed only by the Conservatives and one Liberal Democrat MSP, is an alternative to the UK bill, which MSPs refused to consent to after a row broke out over repatriation of powers from Brussels upon Brexit.

But the law has been referred to the Supreme Court on the basis the UK government thinks it is ultra vires and outwith the competence of the Scottish Parliament.

Mr Wolffe has said the bill was “carefully framed” not to infringe EU law and that it was based on the UK’s bill.

Within the bill are provisions such as retaining the EU’s Charter of Fundamental Rights and EU laws with which ministers could “keep pace” after Brexit.

Lord Keen said it was “perfectly clear” the Scottish bill was “directly inconsistent with the UK Act at the most basic of levels”, suggesting that “the two simply cannot stand together”.

The Lord Advocate’s submissions will argue that UK law officers have made an “erroneous analysis of the legal consequences of withdrawal from the EU”.

John Larkin, Northern Ireland’s Attorney General, previously lent his support to the Scottish position.

“All of its provisions are within the legislative competence of the Scottish Parliament and this reference should be disposed of accordingly,” he said.

Photo credit: UK Supreme Court