Whitehall is taking legal action against the Scottish Government after Holyrood passed a Bill to place the UN Convention of the Rights of the Child on the law books.
The UK Government claims sections of the Bill impact on reserved matters and are beyond the scope of the Scottish Parliament.
A second Bill, the European Charter of Local Self-Government (Incorporation) (Scotland) Bill, is also similarly beyond Holyrood’s powers, according to the UK Government.
Scottish Secretary Alister Jack wrote to the Scottish Government with concerns about the legislative competence of the UN Convention on the Rights of the Child (Incorporation) (Scotland) Bill and the local government legislation, before they were passed, stating they could place legal duties on UK ministers.
However, none of the amendments he suggested were made to the legislation, and both Bills were passed unanimously by MSPs in March.
The UNCRC Bill is intended to give enhanced legal protection to children by obliging public authorities to respect their rights and comply with UNCRC requirements, while the local government Bill aims to protect the basic powers of councils with regards to their political, administrative and financial independence.
Neither Bill has received royal assent to become law because of the referral to the Supreme Court by Mr Jack.
The case is due to be heard virtually on Monday and Tuesday. UK Government sources have reiterated their concerns are purely on the “legislative competence rather than the policy substance” of the Bills.
The concerns focus on certain sections of the new Bills, which the UK Government believes give extensive powers to scrutinise and interpret primary legislation passed by Westminster, which is beyond the scope of Holyrood’s powers.
A second issue is that if the Bills are able to be “read down” so as to make them become legally competent, the UK Government believes this could effect the implementation of a section of the Scotland Act 1998.
A UK Government spokesperson said: “UK Government law officers have referred two bills from the Scottish Parliament to the Supreme Court under Section 33 of the Scotland Act 1998.
“The UK Government law officers’ concerns are not about the substance of the legislation, rather whether parts are outwith the legislative competence of the Scottish Parliament.
“We will be setting out our case in full at the hearing.”
The Supreme Court could uphold the Bills as competent or send them back to Holyrood for amending.
SNP ministers have said the legal action is a “blatant power grab” by Westminster, with the party’s Westminster leader Ian Blackford raising it at Prime Minister’s Questions, accusing Boris Johnson of “shamefully” taking the Scottish Parliament to court.
Afterwards Mr Blackford was rebuked by the Dean of the Faculty of Advocates, Roddy Dunlop QC, who said: “It is not 'shameful' for this challenge to be brought.
“No-one queries the rights of children. The question is the competence of the Scottish Parliament.”
In response Nicola Sturgeon said: “Everybody’s entitled to his opinion. It doesn’t necessarily mean he is right and my opinion on this is wrong. It’s a Bill within devolved competence.”