Westminster asserts that under the Scotland Act, the UK government would need to make a so-called section 30 order to permit a referendum. Such an Order in Council was issued in the wake of the Edinburgh agreement between Westminster and Holyrood in advance of the 2014 poll.
The government under Prime Minister Boris Johnson asserts that, in the interest of stability, important decisions of this kind should only be taken once in a generation. The Scottish First Minister, Nicola Sturgeon, counters that a section 30 order cannot be reasonably refused. Indeed, her governing Scottish National Party (SNP) has pledged to hold an independence referendum still this year, after the May elections in Scotland.
The assertion that referenda can only happen once in a generation is not backed up by practice elsewhere. For instance, only last year New Caledonia repeated its referendum on independence from France merely two years after the initial poll of 2018. Continued association with Paris won on both occasions.
In fact, holding a second referendum after some seven or, in actual fact perhaps more likely, eight years, seems quite reasonable in a democratic society. This would be two full electoral cycles for most states. In addition, Scotland can point to the fundamental change in circumstances brought about by Brexit.
The UK as a whole opted to leave the EU with a slim majority of 51.9 to 48.1 per cent. In Scotland a more sizeable majority of 62 to 38 percent expressed itself in favour of remaining. Moreover, Nicola Sturgeon claims that the views from Edinburgh were not represented as fully in the Brexit process as had been agreed with Downing Street.
Scotland can also appeal to the principle of self-determination in international law. This principle was recently affirmed once more by the International Court of Justice in the Chagos Islands advisory proceedings brought by the United Nations General Assembly in relation to the UK. However, that case concerned a colonial territory. Colonial peoples enjoy a positive right to independence, even if the metropolitan state resists.
It is disputed whether this right also applies outside of the colonial context. But at least in this instance it cannot be doubted that Scotland is inhabited by an established nation historically tied to a clearly defined territory. Through devolution this distinct and territorially defined population has demonstrated the ability to govern itself.
In a few cases, the right of a constituent part of a state to secede is actually made express in the constitution. Examples vary from the former Soviet Union to present-day Ethiopia and the Principality of Liechtenstein. In the case of Scotland, the right to leave is established informally in UK constitutional practice. International law recognises such a constitutional grant of authority, whether made express in the constitution or implied in constitutional practice. This internal, constitutional entitlement is then reflected in the international law doctrine of constitutional self-determination.
However, this doctrine is fairly narrowly framed. Unless the contrary is expressly indicated in a constitution, it does not appertain to entities below the level of territorially distinct nations of a composite state. This excludes, for instance, the Shetland islands. The islanders have threatened to secede from secession. If Scotland leaves the UK, they assert, then they will leave Scotland.
But according to the legal doctrine of uti possidetis, the right to self-determination through a referendum outside of the colonial context applies only to larger, constitutionally recognised units—in this instance Scotland as a whole. In this sense, the EU ruled that the ethnic Serb regions within Croatia and Bosnia Herzegovina could not separate from those two nascent states at the point of their independence from Yugoslavia.
There are exceptions to the uti possidetis principle, such as historically unique circumstances or a specific grant of a separate legal identity from the central government. These might apply to, say, Gibraltar or the Faroe Islands, but they are not relevant to the Shetlands. Still, whether Holyrood heads for independence or not, the Scottish authorities would be well advised to listen the islanders claim that their concerns have been ignored in the process of Scottish devolution.
Where self-determination applies, the way to implement the principle is generally a referendum. In a few cases, like the independence of Bahrain, it was deemed sufficient to offer a popular consultation instead. Slovenia and the Czech Republic dissolved Czechoslovakia through parliamentary decisions, instead of holding a referendum. They did so after parliamentary elections had been fought and won on an independence platform within both entities.
Hence, if it is clear that Scotland is entitled to opt for independence, and if the means to do so is through an act of will of its population, then it follows that the central government should not be able to obstruct the implementation of that right by refusing a referendum.
This was the issue in the recent confrontation between Spain and Catalonia. However, the Spanish constitution expressly prohibits secession, denying a claim for constitutional self-determination. Here it is uncontested that Scotland can go if its people wish it. Yet, even in view of the different constitutional position, the heavy-handed use of police and militia to obstruct the referendum held in defiance of Madrid was rather questionable.
Madrid was able to suppress an act of popular will in the knowledge that no other European state would interfere in what was seen as an internal affair of Spain. But might does not make right. The authority to govern is based on the will of the people. At least within democratic Western Europe, it ought to be inconceivable that an entire, distinct population should be prevented from exercising its will in a genuinely democratic process through intimidation and force.
Of course, Boris Johnson will not deploy the Guardia Civil off the coast of Scotland. Rather, it is likely that the question of a second referendum will be addressed by the Scottish Court of Session and then by the Supreme Court. And there still remains the option of an informal assessment of the will of the people through a consultative process instead of a formal referendum.
The Canadian Supreme Court has clarified in relation to Quebec that the central authorities cannot remain indifferent to the will of the people within a federal-type unit of a state, once this will has been expressed. Instead, it must negotiate in good faith about implementing the people’s voice.
There are however four conditions. First, the referendum question must be clear and unambiguous. Evidently this was the case first time around. There may however be an issue this time.
A referendum tends to narrow an issue down to a binary choice: yes or no to independence. In the ordinary run of things, it would be preferable to have a clear alternative to independence to hand when a referendum is held. However, this alternative vision is yet to be defined.
Michael Gove announced last year that the Cabinet Office he leads would develop broad constitutional alternatives for Scotland. Sir Keir Starmer, the Labour leader, has appointed notable Scot and former Prime Minister Gordon Brown to lead a major consultation exercise about the future of the UK constitution, including Scotland’s future. It is not clear when these alternative plans would be ready. And what if, as seems likely, the proposals offered by the Conservatives and Labour differ significantly?
Second, the referendum process must be open and inviting to all sides. The EU Badinter Commission found in relation to the former Yugoslavia that opponents of independence must be allowed to campaign and to participate on equal terms with proponents. This requirement was evidently violated in 2014 when Crimea supposedly expressed itself in favour of joining Russia.
Where this second condition is fulfilled, the unionists cannot obstruct the referendum through a boycott. The vote will count, even if they chose not to participate, unless total voter participation falls below a reasonable percentage.
Third, the result must be clear. In most cases, this has required a simple majority of 50 per cent plus one vote. However, in some other cases, the sides have agreed that a decision of such importance requires a higher threshold of, say, 55 per cent in favour of independence. This was the case when Montenegro left the Union with Serbia in 2006.
And fourth, even if the pro-independence side wins, it cannot simply walk away and declare independence. It, too, must take account of the interests of the other side and negotiate in good faith about a balanced and reasonable divorce settlement.
In the case of Scotland, extra caution will be required. Scotland can only achieve its goal of independence within the European Union if it is seen to have gone through an entirely consensual process of self-determination, including a divorce among peaceably consenting adults. Otherwise, it is virtually guaranteed that the members of the EU opposing any case of secession as a matter of principle will veto Scotland’s application to join the EU. Cyprus, Greece, Romania, Spain, and Slovakia have persistently refused to recognise Kosovo as a state, despite the contrary position of most other EU members
In short, whatever the rhetoric of the upcoming Scottish elections, both sides will in the end need to engage with one another with respect, in a spirit of accommodation and compromise.
It will not be possible to deny a referendum indefinitely. On the other hand, Scotland can only succeed as a state within the EU if it can demonstrate that it has obtained the fullest consent from Westminster for its potential journey towards independence. This gives both sides equal weight in the discussions that will follow upon the elections in May.
Marc Weller is Professor of International Law and International Constitutional Studies in the University of Cambridge and a barrister at Doughty Street Chambers. He served as adviser in many self-determination disputes around the world and has widely published in this area.