TWO Holyrood Bills passed unanimously by MSPs would give Scotland’s courts “unparalleled” powers to strike down past and future legislation from Westminster, the country’s highest court has been told.

Lawyers acting for the UK Government said the similar pieces of legislation would “trump” existing and future Westminster laws, despite Westminster being the sovereign parliament.

That would be a “subversion” of devolution, in which the Scottish Parliament’s powers are limited, five justices were told.

The claim came at the start of a two-day hearing into whether the Bills stray beyond Holyrood’s legislative competence.

The Supreme Court could uphold the Bills as competent or send them back to Holyrood for amending.

Neither Bill can become law in Scotland until after the outcome of the legal challenge.

In March, MSPs unanimously passed the United Nations Convention on the Rights of the Child (Incorporation) (Scotland) Bill, which would incorporate a UN treaty into Scottish law, which would require public authorities to respect children and young people’s rights.

It also would let children, young people and their representatives go to the courts to enforce their rights, and allow courts to strike down legislation that is incompatible with the UNCRC.

Scottish Secretary Alister Jack had previously flagged concerns the legislation could stray beyond Holyrood’s existing powers.

However deputy First Minister John Swinney dismissed the approach as “menacing” and a “power grab”, and the legislation was passed regardless.

The UK law officers, the Attorney General and Advocate General for Scotland, then challenged the Bill and a similar one incorporating an EU Charter on local Government into Scots law.

They argued “both Bills would bestow upon the Scottish courts extensive powers to interpret and scrutinise primary legislation passed by the sovereign UK Parliament”.

As that would modify Section 28(7) of the Scotland Act 1998, which states Holyrood’s power to make laws “does not affect the power of the Parliament of the United Kingdom to make laws for Scotland”, they argued parts of the Bills were therefore “outside the legislative competence of the Scottish Parliament”.

The UK law officers also sought the court’s guidance on the correct reading of the Bills to ensure they are within Holyrood’s legislative competence, “if such a reading is possible”.

Sir James Eadie QC, for the UK law officers, yesterday told the court the case concerned “whether the Scottish Parliament has the legislative competence to subject acts of the UK Parliament with the need to comply with the UNCRC and to assign or delegate to the Scottish courts powers to strike down, rewrite or declare incompatible provisions of the acts of the sovereign UK Parliament”.

In written arguments, he said: “Both Bills, in slightly different ways, purport to bestow upon the Scottish courts extensive and, in part, unparalleled powers to interpret and to scrutinise the legality of primary legislation passed by the sovereign UK Parliament at Westminster.”

The barrister continued: “The Scottish Parliament is purporting to require Acts of the sovereign Parliament to meet a test to which Parliament has not assented and which may indeed conflict with a purpose Parliament is seeking to achieve.”

In oral argument, Sir James said: "There are, we submit, manifold and obvious competence problems.

“The relevant Bills subject Acts of the UK Parliament, both past and future, to what is in effect characterised as a superior body of law, the UNCRC and the European Charter.

“It does so in circumstances in which those UK parlimanrtary Acts are not so subject to the authority of the sovereign parliament. The Bills do not restrict the introduction of the UNCRC in that way to legislation of the Scottish Parliament only.”

Sir James also stressed the Lord Advocate, the Scottish Government’s rtoplaw officers, had failed to challenge the importance of Section 28(7) in a previous Supreme Court case about a Holyrood Bill on the Continuity of EU law in 2018 and Holyrood’s powers.

He said the Lord Advocate was now arguing that Section 28(7) was "merely declaratory", whereas it was actually key to the Court's consideration.  

In written arguments, James Mure QC, for the Lord Advocate, said none of the provisions modified the law on the relationship between the powers of Westminster and Holyrood “on a proper reading”.

He also argued that if the application of part of one of the Bills would be beyond the scope of the Scottish Parliament, it would be read narrowly to keep it within its legislative powers due He accepted Westminster was the sovereign parliament and could legislate in devolved areas if it chose, but added the “constitutional paradigm” could change over time.

He said: “The basic principles of the constitution is that they have changed in the important sense since 1997.. that there is now a body established by law, the Scottish Parliament, which has the power to repal and to amend Acts of the Westminster Parliament.

“Within legislative competence at least, Acts of the Scottish Parliament cannot be regarded as hierarchically inferior to Acts of the Westminster parliament, because within legislative competence both effectively have supremacy in the legal system in Scotland.”

He added that for Holyrood to legislate “consistently” across the Scottish statute book, it should be able to “condition the continuing legal force and effect” of Westminster Acts of Parliament so “they fit with the policy decided by the Scottish Parliament”. 

Mr Mure was twice interrupted by Court president Lord Reed, who on one occasion sounded frustrated at his inability to answerr a question about the UNCRC Bill’s jurisdiction.

In particular, whether it would apply to tribunals held or appealed to in England.

After Mr Mure said the Bill would apply to Westminster legislation “if the matter was subject ot Scots law,” Lord Reed said: “Well is it or isn’t it? I’m asking you what the jurisdictional scope of this legislation is.” 

Mr Mure is due to finish today, followed by a submission from Wales’ Counsel General.

SNP MSP Neil Gray said the UK Government was attempting a “power grab”.

He said: “They clearly care more about exercising unfettered power over Scotland than they do about the rights of children. The only way to protect Scotland’s Parliament and its powers from this Tory onslaught is with the full powers of independence.”