The UK Government has insisted “there is nothing sinister” about the law which Scottish Secretary Alister Jack used to block Holyrood gender reforms  

David Johnston KC said Section 35 of the Scotland Act was a “key feature of the devolution settlement” and part of the machinery of government in the UK.

He was speaking at the end of the first day of a three-day judicial review hearing at the Court of Session on whether Mr Jack’s veto was lawful.

Mr Johnston told judge Lady Haldane: “There's nothing sinister about this power. This is part of the scheme - it cannot be emphasised too strongly - that it's part of the scheme of the [Scotland] Act. 

“It's part of the machinery by which government in the United Kingdom operates. 

“So that on the one hand, it enables the Scottish Parliament to work within its competence. 

“And on the other hand, it empowers the Secretary of State, on limited grounds, to intervene when there's a concern about adverse effect on the operation of the law applying to reserve matters.

"It’s not an unusual provision. It’s part of the whole scheme.” 

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The Scottish Government is challenging Mr Jack’s decision to use a Section 35 order in January to stop the Gender Reform Recognition (Scotland) Bill from becoming law.

It was first time such an order had been made in the 24 years of devolution.

The Bill, passed by MSPS 86 to 39 in December, is intended to make it simpler and quicker for someone to change their legal sex by obtaining a gender recognition certificate (GRC).

Mr Jack argued the Bill, although within Holyrood’s competence, would nevertheless have adverse knock-on effects on reserved areas of law, including equality law.

Earlier, Lord Advocate Dorothy Bain KC, for the Scottish Government, urged Lady Haldane to strike down the order on the grounds it was unlawful, unreasonable and irrational.

She said Mr Jack had made a material error in law in considering the Bill “modified” reserved law, an essential condition for the use of the Section 35 power.

She argued the UK Government was misusing the power because of a policy disagreement with the Scottish Government, not because of any genuine problem with reserved law.

However Mr Johnston said he disagreed with the Lord Advocate on that point.

He said: “We agree this case is not about the merits of the policy to which the Bill gives effect. But I think that may be about as far as we agree.

“This case is not, as the Lord Advocate would have it, it’s not about a policy disagreement between the Scottish and the United Kingdom Government. 

“Secretary of State's concern is set out in the reasons in the order under challenge. 

“And his concern is that if enacted the Bill would have adverse effects on the operation of the law as it applies to reserved matters.”

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He also disagreed with Ms Bain’s argument that Mr Jack should have had regard to far more information and from far more perspectives when he made his decision.

He said Mr Jack was focused on protecting the interests of the United Kingdom against adverse effects on the operation of the law in relation to reserved matters.

That was very different from the work of the Scottish Parliament on the GRR Bill, he said.

However he accepted the Scottish Secretary did have to comply with the so-called Tameside duty, under which decision makers must take reasonable steps to acquaint themselves with relevant information, and therefore did need materials before him to make his decision.

Ms Bain argues Mr Jack failed to make sufficient effort to inform himself in a balanced way.