Johnson can block a Scottish independence referendum – but that will not secure the long-term future of the UK

The 2021 Scottish parliament election has placed the future of the union at the top of the political agenda. The Scottish National Party (SNP) has fallen narrowly short of a majority in the 129-seat Scottish parliament, but with 64 MSPs, combined with eight Scottish Greens, there will be a clear pro-independence majority in Holyrood. So what happens next?

Even before election day, the Scottish and UK governments had signaled their initial moves. On the SNP side, Scottish first minister Nicola Sturgeon has called upon Westminster to accept the mandate provided by the election result and to pass legislation empowering the Scottish parliament to hold a referendum at a time of its choosing. But Boris Johnson has already indicated that he will reject this request.

A referendum held without Westminster agreement could be blocked in court

The SNP's 'Plan B' is to legislate for a referendum even in the absence of Westminster agreement. A draft bill has already been published by the Scottish government[1] setting out plans for a referendum asking Scots the same question used in 2014: Should Scotland be an independent country?

But if passed at Holyrood without Westminster agreement, the bill would almost certainly be referred by the UK government to the UK Supreme Court. The question for the court would be whether the bill falls outside of the devolved legislative powers, in which case it would not become law. The test would be whether the bill “relates to” matters that are reserved to Westminster,[2] including “the Union of Scotland and England”.[3] And the assessment made “by reference to the purpose of the provision, having regard... to its effect in all the circumstances”.

On a prima facie basis, the Scottish government would appear to face an uphill struggle in persuading the court that a referendum on independence does not relate to the union. What else could its purpose be said to be? A strong hint to that effect was recently dropped by the Court of Session in Scotland, which was asked to assess whether the Scottish parliament could hold a referendum under its existing powers. The Scottish court declined to answer the question, stating that the case was “hypothetical, premature and academic”.[4] Nonetheless, it noted that based on previous jurisprudence, the Supreme Court would block any Scottish bill that has “more than a loose or consequential connection” with reserved matters such as the union. “Viewed in this way”, the Scottish court continued, “it may not be too difficult to arrive at a conclusion, but that is a matter, perhaps, for another day.”

Westminster could legislate to block a referendum – though this would be contentious

The Supreme Court might reach a different conclusion, of course, for instance if it were persuaded that a referendum were just a test of public opinion and so did not in itself “relate to” the union. But in a scenario where the court ruled in the SNP’s favour, or even if the UK government determined that it might lose the case, then the latter could pass legislation at Westminster to block the referendum directly. Specifically, it could amend the powers of the Scottish parliament to make crystal clear that any form of referendum on independence falls definitively outside the scope of devolved powers.

This optics of this approach would not be ideal, and the prime minister would no doubt prefer the court to do the job for him, to avoid the inevitable charge that he was over-riding both the will of the Scottish people and the law of the land. But in legal terms, it is not clear what recourse the Scottish government would have. The UK parliament has amended the powers of the Scottish parliament without its consent on three occasions, most recently via the UK Internal Market Act. It could do so again on this issue if it were willing to take the political hit in Scotland. Given how high the stakes are, it probably would be.

So what other cards does the Scottish government hold? One idea is that Scotland might look to the international community for support, by appealing to the right of national self-determination, which is recognised in the United Nations Charter. However, the right to secede from a sovereign state is usually recognised only in cases of colonialism, political oppression or human rights violations. Absent such extreme circumstances, the international law principle of territorial integrity is likely to prevail.

All this goes to show that the SNP's intended path to independence is strewn with obstacles and pitted with potholes – unless the UK government accepts Scotland's democratic right to vote on independence.

Unionists will eventually have to win the battle for hearts and minds in Scotland

As a result, many unionists will be expecting and supporting a blanket 'No, nay, never' response from the prime minister to pressure from Edinburgh to allow a second referendum. If he does take this line, he will probably secure his objective of maintaining the integrity of the union.

For now, at least.

But looking further ahead, the question for the prime minister to consider is whether the UK can function effectively, and retain its legitimacy as a nation state, on the basis of the UK parliament simply using its sovereignty to compel Scotland to remain within the union, irrespective of the wishes of its citizens.

As things stand, public opinion in Scotland is evenly divided on independence – and unionists might well expect to further erode support for independence once the weaknesses of the economic and fiscal case for it are exposed to the light. But to shut the door on any legal route to independence would risk driving more voters into the nationalist camp, particularly if combined with a growing willingness to encroach upon devolved political autonomy in other ways.

So the prime minister can kick the can down the road, and perhaps by quite some distance. But in the long run, the union cannot hold unless a majority of voters in Scotland, and indeed in each part of the UK, are persuaded that their interests are best served by remaining part of this family of nations. The government now desperately needs a strategy for how it will fight and win that battle of hearts and minds.