While there may be some considerable huffing and puffing in Downing Street ultimately it seems likely that agreement on a further poll will be reached. But what should such an agreement look like?
The Edinburgh agreement of 2012, which set up the 2014 referendum, offers some guidance. It consists of three parts – a brief framework agreement, a memorandum that sets out the agreed modalities of the referendum, and the draft for the Order in Council which formally legalised the process.
Any agreement with Westminster after May will need to cover these items and, if possible, more. First, the agreement would establish the authority of the Scottish Parliament to call for, and conduct, a referendum in deviation from the Scotland Act 2016.
Then, there would need to be agreement on the date. Here both sides will haggle. The UK government may hope that any momentum towards independence evidenced in the opinion polls just now may die away as time passes and as it collects the rewards of its successful Covid-19 vaccine campaign.
Moreover, the unionist parties are at present not even close to articulating a common vision for a reformed, but united, Britain that could be presented as an alternative to independence.
A result that is accepted
The SNP, on the other hand, is committed to an early referendum. Covid offers an avenue towards a face-saving compromise. They might agree that a referendum cannot reasonably take place before 2022 and that it must take place before the end of 2023.
There will be little difficulty in replicating the practical provisions concerning the role of the Electoral Commission, campaign fairness and financing, access to broadcasting spots, etc. Given its opposition to the second referendum, Downing Street may well seek to include an undertaking that no further referendum shall take place for a decade or more.
In 2012, there was some debate about the referendum question. Some thought that a range of options should be considered: the status quo, more devolution, federation, or independence.
In the end, it was agreed that there would be only one alternative, independence or not, clothed in a question that would be "fair, easy to understand and capable of producing a result that is accepted and commands confidence”. The question would be drafted by Edinburgh but independently reviewed.
Westminster would now need to determine whether the alternative to independence would again simply be continued devolution, or whether it would wish to offer a future federation instead. If it is the latter, should reference be made to this vision in the question?
Who can vote?
Next, who is the electorate – who is a Scot for the purposes of the referendum? Is it the pedigree of the individual or simply place of residence?
Other countries have traced the place of birth or even family lineage and linguistic competence of those wishing to participate. Such criteria are sometimes used to disenfranchise residents who have only recently moved into the territory, or conversely to enfranchise members of the diaspora who have permanently moved abroad or been forcibly displaced.
Of course, any ethnic criterion of Scottish family lineage would be rejected by all sides in this instance. The electorate would simply extend to permanent residents of Scotland.
The 2012 agreement ruled that Scotland could include all those permitted to vote in local elections. Under EU law, as it then was, this included non-citizens resident in Scotland. In fact, in 2020, Holyrood extended the franchise to all non-nationals with leave to remain, including refugees.
Cabinet Secretary Michael Gove caused a stir when he refused to rule out that the franchise might be extended to the 795,000 or so individuals born in Scotland but permanently resident in other parts of the UK – a constituency largely thought to favour continued union.
If it is accepted that anyone who is entitled to vote in Scotland can also vote in the referendum, the question remains: entitled to vote in which elections held in Scotland? For the elections in Scotland to the Westminster Parliament, the minimum age is 18. In relation to the Scottish parliament and local elections, the voting age is 16.
It is presumed that the young will largely favour independence. However, as it was agreed to accept 16 as the age requirement in 2014, this solution is likely to be adopted once more.
A road-map and timetable
The 2012 agreement does not say much about the consequences of the referendum. It simply confirms that “the two governments are committed to continue to work together constructively in the light of the outcome, whatever it is, in the best interest of the people of Scotland and the rest of the United Kingdom”.
This sounds rather weak. The Northern Ireland settlement contains at least a commitment by Westminster that any referendum result there would be translated into the legislative acts necessary to implement it.
Of course, there were no doubts in 2014 that a decisive referendum favouring independence would be implemented. Yet, experience elsewhere suggests it is wise to agree at least a road-map and timetable for implementation in case the independence campaign succeeds.
This would include a mechanism to resolve state succession issues. These include questions of ownership of state property, the assignment of state debt to the two sides, pensions, security and the armed forces, recognition of educational certificates, choice of citizenship for individuals on both sides of the border, etc.
This tends to take between two and five years, allowing Scotland to adopt its constitution and other laws.
To prevent deadlock, it is wise to foresee establishment of an arbitration mechanism to settle issues where agreement is difficult. Moreover, Holyrood would need an assurance that Westminster will pro-actively support Scotland’s campaign for EU membership before independence occurs.
Marc Weller is professor of international law and international constitutional studies at Cambridge University