AROUND 5 o’clock on August 17, 2021, a group of 20 protesters “seized” Edinburgh Castle. When questioned, the group asserted public ownership over the building and explained they were “restoring the rule of law,” and “using Article 61 of the Magna Carta” to “claim our power back”.

This declaration attracted not only the attention of local police officers, but considerable ­sarcastic ­commentary on social media. The protesters’ ­invocation of Magna Carta even mobilised fact-checking websites to debunk the constitutional analysis underpinning this impromptu and unarmed siege of the historic site. As Magna Carta was ­ratified by King John some 500 years before the Act of ­Union, has never formed part of Scots law and was largely abrogated in England and Wales in the 19th ­century, it was easy for Scottish lawyers to take umbrage at the fact these protesters hadn’t also seized the ­opportunity to find eccentric legal justification for their actions in more appropriate sources.

Misread or unread, the 1320 Declaration of ­Arbroath, the 1689 Claim of Right, the 1707 Act of Union – or even the Court of Session’s 1953 ­judgment in the case of MacCormick v Lord Advocate – would work just as well as the pseudo-source of legal ­authority justifying their reclamation of Edinburgh Castle on behalf of the plain people of Scotland.

Invoking any of these sources would at least have reflected the traditional independence of the ­Scottish legal system within the UK. It is easy to dismiss these Magna Carta protesters as oddballs, cranks and ­weirdos. Their legal analysis certainly left a good deal to be desired. But their intervention was an ­unconventional reminder that what we understand by the British constitution is not only politically ­contested, but remarkably difficult to pin down.

When the Prime Minister makes it up on the fly and gets away with it, why shouldn’t a gaggle of ­anti-vaxxers dig out their own medieval take on ­Britain’s basic law? If Dominic Raab and Jacob Rees-Mogg are prepared to roll out Magna Carta to justify the repeal of the Human Rights Act, why shouldn’t everyone get in on the game?

The National: Jacob Rees-Mogg

What passes for the British constitution is ­famously uncodified and largely unwritten, a make-work of rags and patches, empty bling and hand-me-down protocol which politicians treat as gospel or guidelines as political expediency tends. The British constitution is the name we give to dignify a bag of stitch-ups and holding positions, confidence tricks, stopgaps and compromises.

It’s a bundle of old parchments, negotiable ­etiquette, conventions more honoured in the breach than the observance, and the all-important royal twaddle – all smoothed sleekly out by the usual channels to create an illusion of dignity, continuity and the impression that anyone knows what the hell is going on. Only the British could imagine that this compromised and often hypocritical mess demonstrates some kind of genius for governing by muddling along.

Of this hollow at the heart of British ­public life, ­Professor JAG Griffith once wrote that “the ­constitution is no more and no less than what ­happens”. “Everything that happens is ­constitutional,” he said, “and if nothing happened that would be ­constitutional also.” The British constitution is expediency in her Sunday clothes (or, on special occasions, in an ermine duffle coat).

READ MORE: Pat Kane: The siren voices of doom are wrong: Scots can build their own future

The one constant is the idea of parliamentary ­sovereignty, and the claim that the ­centre enjoys unlimited unilateral power to build or dismantle whatever it wishes. From the perspective of orthodox UK constitutional theory – of which ­Supreme Court president Lord Reed is one of the most orthodox proponents – the only ­sovereign formally recognised is the ­King-in-Parliament.

As Tom Nairn points out, a ­“peculiar mysticism attaches to the notion” in ­British politics. By transforming the ­feudal monarchy into parliamentary rule dominated by aristocratic and ­patrician interests, the revised vision of ­parliamentary sovereignty established an “extraordinarily centralised apparatus of power and administration” in the UK.

Westminster’s “right to make or ­unmake any law whatsoever” is the central myth around which the rest of British politics is maintained – and increasingly disrupted.

Perceived qualifications on this unlimited sovereignty have prompted a series of counter-revolutionary moves over the past decade.

It was abstract obsessions with the loss of Westminster’s ­sovereignty which helped undermine the UK’s participation in the European ­Union. The potential for its policies ­being reviewed by the European Court of ­Human Rights continues to rankle.

The National: An independence supporter awaits the verdict outside the Supreme Court yesterday

Even the institutions of devolution sat and sit uncomfortably in this constitutional worldview. Only the formal subordination of the devolved parliaments to Westminster – which the Supreme Court has strengthened in recent cases – keeps the show on the road. Westminster needs to feel that power devolved is power ­retained.

But this Diceyan framework is ­constitutionally contested, and has been contested for half a century by ­politicians, activists and campaigners on both sides of the debate about ­Scottish ­independence. In rallies at the other end of the Royal Mile last week, you heard ­another – ­completely mainstream – ­dissenting ­constitutional ­tradition, which to the ears of the ­orthodox ­British ­constitutional law, sounds just as ­misconceived and seditious as the ­Edinburgh Castle ­protesters’ talk about restoring the rule of law.

The idea that the Scottish people have the right to self-determination – including the right to bring Scotland’s entanglement in the 1707 Union to an end – is one which is now deep-rooted in constitutional ­practice, constitutional discourse and popular constitutional understandings of Scotland’s status in the United Kingdom.

In 1989, the pro-devolution Campaign for a Scottish Assembly set out a Claim of Right to which every Labour and LibDem MP ­representing ­Scottish ­constituencies – with the notable ­exception of Tam Dalyell – put their names.

This modern Claim of Right ­unapologetically asserted the “sovereign right of the Scottish people to determine the form of Government best suited to their needs”.

The language of self-determination undergirded the decision to establish a Scottish Parliament in 1998, and the role of the referendum in sanctioning its ­creation. A commitment to popular ­sovereignty is routinely invoked at the ­beginning of each new session of the Scottish Parliament, and by Scottish MPs in the Westminster Parliament too.

Over the past decades, politicians ­in the SNP, Green, LibDem and Scottish Labour parties have freely ­associated themselves with the idea ­without embarrassment. You can’t help but notice who’s blushing now.

And yet as profoundly as this constitutional idea has shaped modern Scottish politics, as central as it has been to the demand for greater self-government ­within and beyond the United Kingdom – it is entirely legally invisible, as ­formally ­invalid as the claim that Magna Carta ­authorises you and me to turf Major ­General Alastair Bruce out of his castle.

Judges will irritably bat away attempts to articulate this argument in legal ­forums. Lawyers will continue to ­worship the old gods of parliamentary sovereignty and the legal fiction that Westminster is the primary cockpit of the nation’s ­affairs, and all other parliaments and assemblies are derivate, secondary and provisional. But the picture painted by the legal relations and the political relations between these ideas and institutions is out of sync with the social reality. It is another ­Scottish Jekyll and Hyde story.

The National:

As former Tory MSP Adam Tomkins (above) has said, in legal terms “the Claim of Right is heresy”. But in Scottish politics, the heresy is orthodox, taken for granted by the majority of people in Scotland. And for a time, it appeared to be ­recognised by British state institutions too. It seemed to understand that unlike the nation states which emerged in the course of recent centuries, the United Kingdom was and is constituted differently, capable of ­unravelling back into its different parts.

Perhaps the most curious aspect of last week’s Supreme Court judgment is that Lord Reed felt it was necessary to say anything about self-determination. While Roddy Dunlop KC described this as “an answer to the SNP’s written case, which needed to be addressed”, the Dean of the Faculty of Advocates well knows this isn’t so. Courts aren’t duty bound to address every argument put to them, particularly by interveners, the justices weren’t prepared to hear from for five minutes at oral hearing.

Judges routinely avoid deciding more than they have to decide to resolve a case. The court could have disposed of the ­indyref reference on the narrow ­devolution point, without sharing any reflections on the limits of self-determination in international law. Indeed, Lord Reed has a bit of a reputation for ­applying Occam’s razor to the legal ­problems ­presented to him, reasoning in the straightest, sharpest line to reach the most economical decision in his cases.

You wonder what provoked the ­digression here, guaranteed as it was to provoke a political backlash, sitting ­uncomfortably alongside the ­assumptions many Scots take for granted about their democratic rights?

You imagine many Unionist politicians might have been grateful if he’d left this passage out. Because this judgment gives the UK Government nowhere to hide.

In past judgments, Lord Reed has been fond of stressing that the ­statutes which established devolution in ­Northern ­Ireland, Wales and Scotland aren’t ­“constitutions”. In legal terms, this ­attitude has usually meant that they ­deserve no more generous interpretation from the courts than the Dangerous Dogs Act.

This approach has resulted in a more restrictive interpretation of Holyrood’s powers, but it also exposes the fact that the Scotland Act is no more solid or l­asting than the Dangerous Dogs Act.

The powers it allocates to or takes away from Holyrood are entirely political, ­alterable by just a few readings of a new bill in Westminster or by asking King Charles to sign one of those famous ­Section 30 orders.

The UK Government can’t credibly say “the constitution says no”, as if the outcome is nothing to do with them and sadly unalterable.

The National: Lord Reed

International law may, as Lord Reed (above) held on Wednesday, not afford Scots the right unilaterally to secede from the United Kingdom, but the belief that Scots have a right to self-determination is a ­social and political fact which opponents of Scottish independence must contend with.

Lawyers will never tire of pointing out when other people get the law wrong. But lawyers also have the bad habit of ­ignoring powerful social facts which don’t fit ­neatly into legal categories. ­Lawyers tend to privilege legal over social facts and act surprised when the world doesn’t fall ­biddably into line.

To argue this assertion of a right to self-determination is somehow ­technically ­inaccurate, and therefore ­disproved, or ­ignorant, or a form of “false ­consciousness” is not only ­objectionable and condescending – it’s a technical trump played to rebut a substantive ­argument. And it won’t work, not least because British constitutional practice has only encouraged and confirmed the idea that this is not a unitary state.

If the British state doesn’t accept that Scots have a right to determine their democratic future, why would they have permitted the 2014 referendum to take place?

If the UK establishment is really convinced Scotland is just another incorporated region of greater Britain “for all time coming”, why did it mistake it for a potential nation-state? If self-determination doesn’t apply here, why did the UK Government feel the need to ask Scots in 1997 if they agreed with the new ­parliament being established? If self-determination is wholly irrelevant to the Scottish national question, why feel the need to argue the Union is “voluntary” at all?

For the UK Government, expecting technical objections to constrain people’s constitutional ideas and aspirations is a fool’s hope.