THE UK Government could strike down laws passed by Holyrood after a Brexit “power grab”, while Scottish policies such as minimum unit pricing for alcohol may be rendered useless, experts have warned.

Boris Johnson’s Government last week unveiled a White Paper on enshrining a UK “internal market” in law, which it claims is necessary to ensure seamless trade between England, Scotland, Wales and Northern Ireland.

Scottish ministers have warned it represents the biggest threat to devolution since the Scottish Parliament was reconvened in 1999.

Writing in the Sunday National today, Brexit Secretary Michael Russell said it means “any and all existing powers can be over-ruled on a Whitehall whim”.

“There isn’t the slightest doubt ... that this is a major power grab designed to undermine the existing devolution settlement and devised by those who want to disable devolution,” he said. Experts told the Sunday National the White Paper is so lacking in detail it is difficult to fully assess what the implications will be.

But what has been outlined has raised major concerns over the impact on devolution and potential for “far-reaching” consequences for Holyrood in the future.

Jess Sargeant, senior researcher at think tank The Institute for Government, said one issue was the need for Westminster to have a mechanism in place to ensure devolved nations would not pass laws in contravention of the internal market principles.

She said: “It is not clear entirely how this would work, this is a hypothetical situation – but for example, say the Scottish Government wanted to pass a bill that banned the sale of chlorinated chicken, despite the fact it was acceptable in England.

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“It would then be likely there would be some kind of mechanism through which that law could be struck down essentially.

“It is likely Acts of the Scottish Parliament could be challenged on that basis.” She added: “The White Paper is not clear how it is going to do it, but if you are going to pass a law in the UK Parliament that says every part of the UK must recognise standards in every other part of the UK, there is going to have to be some kind of way it prevents the devolved legislators passing Acts which are in direct contravention of that principle.”

The proposals have gone out for consultation for four weeks, and it is expected the UK Government will bring forward a bill in Autumn when Westminster returns from recess. With Johnson’s refusal to extend the Brexit transition period, the clock is ticking down to have the legislation in place before the deadline of the end of the year.

It is an extremely tight timetable for implementing a system which has been the subject of intense work and negotiations since the Brexit vote in 2016 – and will have major repercussions for years to come.

Michael Dougan, professor of European Law at the University of Liverpool, described the proposals published last week as “sketchy”.

“There is an enormous amount of detail which is just missing,” he said. “So it is genuinely quite difficult to work with this White Paper as a set of concrete proposals. That in itself is a major criticism.

“The Scottish Government and Parliament and the Welsh Government and Parliament – and the rest of us – have a right to be able to participate in and comment on these incredibly important constitutional developments, without just a couple of weeks to try and influence their content.”

He added: “This whole process of designing the UK internal market has taken several years of negotiation and thinking and lots of teams of hardworking civil servants in the different administrations trying to bash out the details.

“Suddenly because Johnson refuses to extend the transition period, this has become urgent.

“And I think this White Paper smacks of the unnecessary urgency which is caused by the refusal to extend the EU transition period.”

Dougan pointed to the “incredibly important” principle of mutual recognition as an example of where the Tory Government has failed to outline vital details.

This principle means that goods which are legally sold in one country can be marketed and sold in any other.

However Dougan said in most internal market systems, it was not an “absolute” and exceptions were allowed if they could be justified as being in the public interest.

“In this White Paper it doesn’t mention what those might be – and it actually suggests there won’t be any,” he said.

“If that is true, basically anything that happens in England is automatically going to be in the shops in Scotland and the Scots can’t do anything about it – so what is the point in having devolved powers to regulate that part of your economy?

“Without knowing that sort of detail, it is incredibly difficult to understand the significance of these proposals.

“If this is an absolute rule of mutual recognition, that is incredibly far-reaching and will have a direct tangible impact on what devolution means in practice.”

Dougan suggested one potential example under this scenario would be that the policy of minimum unit pricing for alcohol would mean “nothing” as the sale of cheaper English alcohol would have to be allowed.

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“If that is the case, it is a perfect example of why would you bother having it? It is effectively rendered unenforceable, all you are doing is penalising your own producers against import competition and you can’t control the import competition,” he said.

“That is what the White Paper suggests, but without the detail it is impossible to know.

“The really key question here is what is the actual content of these proposals before we can make assumptions about particular examples. But the overall thrust of them is very far-reaching.”

Dougan said he could “fully understand” the concerns of the Scottish Government over the proposals.

“This isn’t about an independence agenda or a not-independence agenda,” he added.

“I think anyone in Scotland who values the ability of Scotland to have control over its own affairs – whether in accordance with the current devolution arrangements or something more ambitious than that – should probably be quite concerned about these proposals.”

For its part, the UK Government insists the proposals represent a “power surge” for Scotland.

It claims the return of powers to the UK from Brussels after December 31 will see the Northern Ireland administration receive responsibility in 157 of the 160 areas, Scotland in 111 and Wales in 70. Cabinet Minister Michael Gove has also insisted “scores of new powers” are going to the Scottish Parliament.

Aileen McHarg, professor of public law at the University of Durham, said it was an argument which looked persuasive if you “don’t really understand how devolution works”.

She said: “New powers are coming, so the constraints that EU law imposed are being lifted in 111 areas.

“But then this other new constraint is being imposed in its place – so these 111 powers plus various other powers may be subject to new and tighter constraints.”

McHarg pointed out that under EU law there was the possibility of using objectives such as protecting public health or the environment to “override” the constraints – but it was unknown if this would still apply under the UK internal market plans.

SHE said: “The risk is it will seriously constrain devolved competencies. People will say it doesn’t make any difference because the devolved parliaments are already bound by EU law and all we are doing is substituting a domestic internal market constraint for an EU market constraint.

“But the scope of these new provisions is likely to be wider than EU law and it also looks like it might apply more strictly than EU law.

“The combination of those two things looks really worrying – this could apply more broadly and more strictly than the EU law constraints. Until we see the legislation, we just don’t know exactly what the impact will be.”

Opposition parties have also warned the Tory Government proposals represent a threat to devolution.

Scottish Greens co-leader Patrick Harvie said it demonstrated the “utter contempt” with which Johnson’s Government treats Scotland.

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“This top-down plan to control the internal market from Whitehall would strip the Scottish Parliament of its ability to legislate in a host of devolved areas,” he said.

“Not only would this proposal undermine Scotland’s right to make our own choices, but it would intentionally put public health measures like minimum unit pricing of alcohol at risk.”

Harvie said the attempts by the Tories to circumvent the powers of the Scottish Parliament were “a disgrace”. “It’s no wonder more people than ever before are ready for Scotland to become an independent country,” he added.

Scottish Labour Constitution spokesman Alex Rowley MSP said it was “nothing short of an attack on the devolution settlement”.

He said: “The Tories claiming their proposals for a UK internal market will deliver greater devolution is disingenuous at best, and a threat to the stability of the UK at worst.

“Surely any internal market should have the full consent of all four nations of the UK, the Tories seem content to railroad through this principle and try to impose their view over devolved administrations – a move that is totally unacceptable.”