WITH this week’s landmark ruling by the Supreme Court, and Theresa May’s Lancaster House speech last week, the phoney war is over and the Battle of Brexit is about to begin. But is the Scottish Parliament already on the casualty list? Its lawmaking powers have been revealed as tenuous and enfeebled, subject to review at the whim of the Brexit Government.

This is not the Supreme Court’s fault. We should thank the Law Lords for drafting a landmark ruling that will be studied by constitutionalists for centuries. They defied the death threats and tabloid taunts of “enemies of the people” and upheld the rights of the people, delivering a textbook account of what Westminster parliamentary democracy means.

The Supreme Court judgment confirmed that the Prime Minister and the Brexiters had launched, in effect, an executive coup by attempting to push through hard Brexit under royal prerogative – the pre-democratic powers of absolutist monarchy. That they didn’t get away with it is down to the Law Lords and Gina Miller, the Guyana-born City fund manager who brought the original action and who is invariably depicted in the tabloid press with a sneer of contempt on her lips. It is to Parliament’s shame that it was left to a private citizen, and not MPs themselves, to fight for the sovereignty of parliament.

Mrs May’s dramatic announcement yesterday of the White Paper on Brexit that she has spent six months refusing to consider is a sign that the coup has been repulsed, at least for now. The tanks are back in the barracks. But it now requires MPs to exercise the authority handed (back) to them by the court. Do they have the cojones ? They’re giving a pretty good imitation of headless chickens, at least on the Labour benches. You have the impression the Labour leader, Jeremy Corbyn, would rather not have had to go to the bother of challenging Brexit.

In Scotland, we should also thank their Lordships for making crystal clear what many suspected: namely that the Sewel Convention, under which Westminster supposedly refrains from ruling on devolved issues without the consent of the Scottish Parliament, is froth, mince, tripe,baloney and codswallop. It has no legal force. The clause in the 2016 Scotland Act, which supposedly placed Sewel on a “statutory footing”, was just there to fool the natives into thinking their Parliament’s powers were “entrenched” and irreversible.

Holyrood’s legislative powers are clearly and explicitly on loan from Westminster and liable to be over-ridden as and when the UK Government chooses. No one will believe a word UK ministers say in future about the powers and constitutional standing of Holyrood; not that many of us did in the past.

Beyond that, notice has been served on Scotland that further wide-ranging changes to Holyrood’s powers could be on the way by diktat from the UK Government. This will be in the wake of the legislative upheaval that takes place when Britain is ripped out of the EU. Of course, in theory, Westminster could block Article 50 and halt Brexit altogether; it has the power. The Supreme Court made clear that the June referendum was, as the Government had said, purely advisory. Only Parliament has the authority to invoke the fateful clause in the Lisbon Treaty that triggers Brexit.

The Liberal Democrats, the SNP and an indeterminate number of Labour and Tory MPs are determined to vote against but they won’t succeed. Labour has already said it will not impede Article 50. Whether any amendments are tagged on is another matter and attempts will be make to keep Britain in the single market. The House of Lords could block Article 50 but, since the Parliament Acts of 1911, it can only delay the process, not impede it.

After Article 50, attention will shift to the Great Repeal Bill, which is to be tabled sometime in the next UK parliamentary session beginning in May. This will be a detailed piece of legislation repealing the European Communities Act of 1972 that took us into the EEC. The Government says that the thousands of directives and regulations from Brussels, on nuclear safety, the environment, workers rights, trading standards and, yes, bent bananas, will simply be imported onto the UK statute book as they stand. It will be as if Britain were still in the EU.

You might wonder why the Government is so keen on leaving the EU if it’s going to keep its laws. But Mrs May wants to strike a quick free trade deal, giving Britain continued access to the single market, without having to accept the “four freedoms” of labour, capital, services and goods. This is the “have-cake-and-eat-it model” strategy revealed in those notes for the business Secretary Greg Clark inadvertently revealed to press photographers in November. The Prime Minister believes that the EU will have no grounds for denying continuing free trade since there is “regulatory equivalence”. British toasters shall not be denied their freedom of movement in Europe.

The 27 member states of the EU will beg to differ. They’ll argue that, if you want to be in this free trading club, you have to abide by the Brussels rules and accept the arbitration of the European Court of Justice. It has nothing to do with the Human Rights Act and is essentially the umpire in disputes over those economic freedoms of labour, capital, goods and services. As with any free trade zone, goods like toasters have to be EU-approved to go on sale without lots of paperwork or tariffs.

From a Scottish point of view, the Great Repeal Bill is double trouble. Scotland will lose economic privileges and valuable inward migration, which is all that has been keeping our population from dwindling. It’s clear that the repatriation of European law could lead, without consent, to drastic changes, too, in the Scottish Parliament’s remit and purpose. Since all of Holyrood’s laws since 1998 have had to be in accordance with the European law, this could have profound consequences. Everything is suddenly up for grabs.

Forecasts of a raft of new powers coming “naturally” to Holyrood after Brexit – fishing, farming and so on – should be regarded as about as dependable as the claims made about the Sewel Convention. Anything important will be reviewed by Whitehall and ruled upon by the UK Government. It is expected that the Prime Minister will resort again to executive powers to alter many of the laws on matters like the environment or food safety, without consultation.

Almost anything can and probably will be altered by the Brexiters in charge at Westminster as it puts together a new single market and sets all the laws that govern it. Holyrood is supposed to exercise primary lawmaking powers, but it is a house on shifting sands, without any kind of sovereign or legislative authority. After this week, Holyrood is no longer a parliament in anything but name.