‘HOLYROOD does not consent to the EU (Withdrawal) Bill”. There you have it: a full blown constitutional crisis – a question of who rules.

This is the first time in 20 years that the Scottish Parliament has said No to a Westminster request to invade its legal territory. It was a decisive vote by MSPs – 93/30 – leaving Ruth Davidson’s Scottish Tories isolated in the chamber, a pretty clear endorsement of Nicola Sturgeon’s dogged determination to defend the devolution settlement as she sees it.

Maybe it doesn’t feel like a crisis, since there hasn’t exactly been rioting in the streets, but it is. Some journalists have professed to be utterly bored by the whole dispute. Which is odd, because it is arguably the biggest political story involving Holyrood since the creation of the Scottish Parliament in 1999.

The outcome of this constitutional tussle could define the parameters of Scottish politics, and the constitution of the United Kingdom, for the foreseeable future. It is also another spanner in the Brexit works, at the very moment when Theresa May’s cabinet is falling apart. If this is boring, I don’t know what they’d find exciting – baby boxes, perhaps.

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Certainly, there’s been a long run-in to yesterday’s vote. This involved a sometimes tedious itemisation of powers – agriculture, pesticides, fish, food standards etc. – and rarified talk about reserved powers, conferred powers, sunset clauses, continuity bills, repatriation and grandfathering. But in essence this is about whether or not the Scotland Act of 1998 actually means what it says about Holyrood’s powers beginning where Westminster’s reserved powers end. Does Holyrood exercise its powers as of right or are they just on loan from Westminster? Is the UK still a unitary state in which the Westminster rules in all circumstances, or should consent be required from the devolved parliaments? It is surely right that this issue should be decided once and for all.

For the Scottish Government could well lose this tussle – indeed, is likely to lose. Yesterday’s vote can be overturned in Westminster since the consent of the Scottish Parliament is only required “normally”, to use the weasel word in the 2016 Scotland Act. But the UK Government will always argue that, when it needs to over-ride Holyrood. Whenever governments say they need to suspend the constitution because of abnormal circumstances, you can be pretty sure that you’re looking at a new normal.

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Ms Sturgeon has been accused of of dogmatism and grievance-mongering, but the UK Government’s own conduct of this issue has been risible. Its proposed amendment to Clause 11, with its “rape clause” definition of consent as happening when there is “no consent” and when “consent is refused”, was a grotesque abuse of language. The truth is that the UK Government has been in a panic. It forgot about devolution until the last minute, and then tried to ignore the constitutional reality that Britain no longer functions as a unitary state in which Westminster can do what it wants.

Ministers are reportedly afraid that if they accept the right of consent they will hand Sinn Fein a veto in Ireland. But this is not the way to resolve the border problem. The Scottish Government has not asked for a veto, only consent, and accepts that there have to be “common frameworks” for things like GM crops, environmental standards and food safety. And yes, that does mean a degree of trust on both sides. The custodians of the 2014 “Vow” promised that Holyrood’s powers would be “entrenched” by placing the Sewel convention – the principle that Westminster cannot legislate on devolved issues without Holyrood’s consent – on a statutory basis. Holyrood, remember, was to become the “most powerful devolved parliament in the world”. If this was all so much nonsense, it’s time we knew.

Or should the Scottish Government just have rolled over and not bothered with all this “troublemaking” and “nit-picking”? Should Ms Sturgeon just have said: “Fish and farming, who really cares? Let’s just accept that the UK Government can take charge of the 111 powers repatriated from Brussels”? Yet that would have set a precedent that would have endured, and would have redefined Holyrood as Strathclyde Region writ large. Conversely, if the Scottish Parliament stands firm on the principle of consent, and wins the day, then it could mean that Holyrood is a real parliament after all.

Analysis: Holyrood's vote means the constitutional row will continue

Ultimately, this involves the entire UK and should be decided by MPs in Westminster, rather than by judges in the Supreme Court. The court is expected to rule on in July on whether the Scottish Parliament has the power to pass a continuity bill, retaining EU law. But devolution is a political matter not a legal one, and MPs should not hide behind judges’ wigs. It would certainly be an abomination if the UK Government were to simply impose consent to the EU Withdrawal Bill without MPs in Westminster being given a proper vote on it.

Most commentators seem to regard it as a foregone conclusion that MPs in Westminster support the Tory Government. But that remains to be seen. I suspect MPs, on both sides of the Commons, realise that the SNP could win here even if it loses. The sight of Westminster imposing its rule over Holyrood, effectively repealing Donald Dewar’s Scotland Act, would instantly become a towering landmark in Nationalist folk memory. A referendum on independence may not be imminent, but when the next one finally comes around, we can be sure that any Unionist campaign will face a brick wall of scepticism to any promises it makes about the future wellbeing of devolution.

Moreover, there are MPs in Westminster who genuinely believe in Scottish home rule, and they may not be happy to see it compromised just for the convenience of the UK Government’s Brexit plans – that’s if it had any plans. They may say that the principle of subsidiarity, that central government should not dictate terms to devolved parliaments, is more important than saving Theresa May’s face. What if Westminster, after mature reflection, decided that, actually, the 1998 Scotland Act had it about right? Let’s stick with that.