The National:

THE European Union has a common market, a single market, in which low-friction trade takes place across the continent. We get tariff free access to as much camembert, gorgonzola, halloumi and feta as we can eat. This Internal Market Bill, in contrast, is pathetically provincial. It sets its sights no further afield than Welsh cheddar and Cornish blue.

Not only is the internal market tiny, it is also tawdry. The European Single Market provides relatively high standards of food safety, consumer protection, workers’ rights, and environmental protection. One of the sticking points in the Brexit negotiations is that the EU – quite rightly – will not allow the UK free access to the Single Market while undercutting these regulatory standards.

In the event of a No-Deal Brexit, however, the UK would be able to reduce these standards. If the Internal Market Bill, now in its final stages in the House of Commons, becomes law, these would be imposed on Scotland by the UK Government.

Aside from the content of the bill, the manner of its passage raise important issues of constitutional propriety. When devolution was introduced, the principle was established that the Westminster Parliament, although retaining full sovereignty in theory, would not normally legislate on devolved matters without the consent of the devolved legislatures.

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Like the other conventions of the UK’s unwritten constitution, this so-called "Sewel convention" was based on a combination of gentlemanly self-restraint and hard-headed political reality. To violate it would be unacceptable in principle, as it would undermine the basis of devolution, but it would be politically suicidal to any UK Government foolish enough to try it: "Nemo me impune lacessit" and all that – no one meddles with me and gets away with it.

One of the recommendations of the Smith Commission, appointed to review the workings of devolution after the 2014 referendum, was to recognise the Sewel Convention in statute.

It is now right there in Section 28 of the Scotland Act 1998, as amended by the Scotland Act 2016: "It is recognised that the Parliament of the United Kingdom will not normally legislate with regard to devolved matters without the consent of the Scottish Parliament."

The trouble lies with that weasel-word "normally". Who defines what is normal? Who determines when deviation from the norm of self-restraint is permissible?

Boris Johnson, as we have seen from the 2019 prorogation of Parliament, might be more willing than previous Prime Ministers to play "constitutional hardball", and to act as if mere conventions could not possibly apply to him.

Regardless of who is Prime Minister, however, the basic structural problem remains. The rules defining and protecting the autonomy of Scotland are not adequately entrenched because the devolution settlement left Parliamentary Sovereignty intact.

In effect, this means that Westminster should not legislate on devolved matters in Scotland, except when the governing majority in Westminster decides otherwise. It is as flimsy a safeguard as can be imagined.

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Countries with genuinely federal constitutions do not work this way. The Canadian Parliament cannot just override the Provincial legislatures, because the Supreme Court of Canada, enforcing the division of powers prescribed by the Constitution, restrains it.

India allows more flexibility, recognizing that sometimes the Union Parliament might have to legislate on matters normally assigned to the States; but the Union Parliament can only do so if the State Legislature consents, or if a Proclamation of Emergency is in effect, or if authorized by special resolutions of both Houses, valid for a limited period.

In the UK, Scotland has no such protection. Such autonomy as we enjoy is entirely at the grace-and-favour of the majority in Westminster. Real federalism could in theory solve that problem, but real federalism is unlikely given the unwillingness of the UK Government to accept restraints on the absolute sovereignty of the Westminster Parliament.

In that case independence remains the only way to ensure that Scotland can protect itself from the Internal Market Bill’s encroachment on its autonomy. Better still, Scotland as an independent country would be free to negotiate its own (better, closer) trade deal with the European Union, pending rejoining the European Single Market in due course.