AT the height of the Supreme Court hearings on Article 50 last week, the Law Lords launched into a debate about the meaning of the word “normally”. The Scotland Act 2016 says that the Westminster Parliament “will not normally legislate with regard to devolved matters without the consent of the Scottish Parliament”. But what does “normally” mean? Who decides what is normal? It was one of those moments when you realise that the law courts are not the best places to resolve questions of political power.

But on the plus side, there are three things we can be pretty certain about as a result of last week's shenanigans in court and Parliament. Brexit will definitely happen, everyone has now accepted that. The Government will, however, almost certainly be defeated on its attempt to force through Article 50 under “royal prerogative” and will have to place a bill before Parliament that can be amended. Third, there will almost certainly have to be a new Scotland Act following Brexit that could remake or destroy the 300-year-old Union.

Their Lordships eventually tired of their semantic disputations and said that vague and subjective words like “normally” had no place in the law. It's what lawyers call a “weasel word”, sneaked into the wording of the Scotland Act 2016 to make it appear to mean something that it doesn’t. The UK Government wanted to suggest that Holyrood could not have its powers altered by legislation in Westminster, when in fact sovereignty had been very firmly retained or “entrenched” in Westminster. In short: the UK Government decides what is normal and what isn’t.

This matters, not least because it has undermined the 2016 Scotland Act even before it has been implemented. The UK Government was trying prevent Holyrood throwing a spanner in the Brexit works by refusing consent to Article 50, which triggers British withdrawal. But two questions arise here: would MSPs refuse consent to A50, and would it matter if they did?

As we saw in the Commons last week, it's perfectly possible to get a majority for leaving the EU in March next year as Theresa May wants. Voters must have been very puzzled that, at the very moment the Lords in the Supreme Court were considering whether or not Parliament had the right to vote on Article 50, MPs were doing precisely that across the road in Westminster. The vote for Brexit was decisive too: 448 votes to 75. So what's the problem?

Well, the problem is that Wednesday’s Commons vote was not, if you’ll excuse the word, normal. The proper way for a government to make profound changes to the powers of Westminster is by what is called primary legislation – in other words a proper bill, usually preceded by a white paper outlining the government's intentions. Last week’s was just a wham-bam-thank-you-ma’am resolution that resolved nothing.

At least that's how the Government's critics see it. Theresa May of course regards the Parliamentary vote as having given MPs precisely the say on Article 50 they said they wanted. It also places on record overwhelming support for the Government's plans to fire the Brexit gun in March. Indeed, many MPs believe Labour was daft to have put the resolution in the first place. The suspicion is that the Labour leadership actually wanted to signal to its voters in the north of England that it is not against Brexit.

All this must have been as mystifying as it was frustrating to the casual viewer. Anyone dipping in and out of the Supreme Court hearings would have been forgiven for thinking that this was some kind of daft legal seminar, where antique judges spent their time arguing – as they did – about the difference between “with regard to” and “relating to”. What has this to do with immigration, jobs, trade deals and citizenship rights in the EU? Not a lot it has to be said.

But the UK Government's semantic jiggery pokery has caused great political damage to the Union. It looks as if the Brexit process is being used to undermine Holyrood and diminish its powers. The Scotland Act 2016 itself appears to many as a cynical attempt to lead Scots into thinking they had something like a federal parliament when they didn’t. The next time a bill is promised that gives Holyrood “extensive new powers” and “entrenches its constitutional status” it will be subjected to such withering scrutiny that it may be impossible to draft anything that can command the confidence of Scottish voters.

And new legislation will almost certainly be required. When the 1972 European Communities Act is repealed, the original 1998 Scotland Act itself will no longer have legal force. This is because Scottish devolution was based on EU law. Every act of the Scottish Parliament has to be in accordance with EU legislation, and Brussels lays down the law here directly on a whole range of matters, such as agriculture fisheries and the environment, which are nominally devolved to Holyrood.

Indeed, taking Britain out of Europe could leave Holyrood with pretty much a clean sheet because so many of its powers have in the past come from the EU. The question then is: who fills in the blanks? It is assumed that none of Scotland's existing powers would be removed as a result of this – but we simply don't know.

The Scotland Secretary, David Mundell, has suggested that agriculture and fisheries will automatically come to Scotland. But Westminster might say they don't want Scotland to have powers, for example, over genetically modified crops since GM is not a “normal” farming issue. Who really believes that the UK replacement for the Common Fisheries Policy will be decided only in Scotland?

Most importantly: what about the revenue streams? Scotland gets 18 per cent of all CAP farm payments, amounting to £425 a year. Is the UK Treasury going to continue writing cheques for that amount indefinitely after Britain leaves the Common Agricultural Policy? I doubt it. Yet, 60 per cent of Scottish farm incomes currently come from the EU.

Before the EU referendum, the then Lord Chancellor, Michael Gove, promised a new era of devolution in which Holyrood could even win powers over matters such as immigration. This now seems like an exercise in post-truth propaganda. Holyrood will have to fight every inch of the way to secure new powers, and guarantee old ones, when the post-Brexit Scotland Bill comes before Westminster sometime after 2019.

Scottish voters won't be fooled again. They're now wise to the ways in which weasel words like “normally” can be inserted into statutes to change their meaning. The next Scotland Act will have to give a cast iron, copper-bottomed assurance that the Scottish Parliament exercises sovereignty in its own right, not just at the whim of Westminster governments. The way countries “normally” acquire sovereignty, of course, is by becoming independent.

If last week confirmed anything, it is that the UK constitution is in a state of flux – at all levels, but especially as the standing of the national parliaments. As the Brexit process grinds on and on, and the constitutional anomalies mount between Scotland and the rest of the UK, there will be many on both sides of the Border who will be saying: stuff it – let's just scrap the Act of Union of 1707 and start again.