Case Comment: Supreme Court rules Scottish Parliament can’t hold IndyRef2 unilaterally

By Prof Rachael Lorna Johnstone
Image: The Lord Advocate, the Rt Hon Dorothy Bain KC, discusses the case before five judges of the UK Supreme Court. 

Prof Rachael Lorna Johnstone
Professor of Law
University of Akureyri (Iceland) and Ilisimatusarfik (University of Greenland)

Case comment: Reference by the Lord Advocate of devolution issues under paragraph 34 of Schedule 6 to the Scotland Act 1998 [2022] UKSC 31 (UK). 23 November 2022.


This case comment is intended to explain the UK Supreme Court ruling of 23 November 2022 about whether or not the Scottish Parliament can authorise a consultative referendum on Scottish independence. It aims to clarify the legal points of the case in ordinary language to aid informed discussion about the constitutional future of Scotland. References are provided for those who wish to delve deeper, and readers are encouraged to read the original judgment of the Supreme Court which is relatively short and written in fairly accessible language.

It reviews the three main arguments before the court. 1) Is the case admissible? (i.e., should the judges even consider the case at all?); if yes: 2) may the Scottish Parliament pass legislation to allow a referendum under the Scotland Act? or 3) may the Scottish Parliament pass legislation to allow a referendum under international law? On this third question, the case comment provides a more detailed account of the international law of self-determination than that considered by the Court and reflects on its application to the case of Scotland.

The following reflections focus on the legal questions. They do not enter into the merits of whether a referendum should be held, let alone whether Scotland should become independent or the political desirability of seeking the ruling at all.


The Scotland Act[1] (re)established a Parliament for Scotland as a devolved legislative chamber for Scotland. It opened on 12 May 1999. The Scottish Government is formed by the party/ies that holds a majority of elected seats.

The Scottish National Party (SNP) is a pro-independence political party established in 1934. The SNP has led the Scottish government since 2007, first as a minority administration, later as a slim majority and currently in a power-sharing agreement with the Scottish Green Party (also pro-independence).

As a devolved parliament, the Scottish Parliament’s competences are limited by the Scotland Act. Certain matters are reserved for the Parliament of the United Kingdom (Westminster). Prior to introducing a new Bill (draft law) to the Scottish Parliament, the Lord Advocate (the top legal officer for Scotland) must “pre-screen” it by assessing that it is compatible with the Scotland Act. In other words, the Lord Advocate reviews all the draft laws to determine if the Scottish Parliament has the power to pass them.[2]

In this case, the Lord Advocate (Dorothy Bain KC) could not state with confidence that the Bill was within the competence of the Scottish Parliament. The First Minister (Nicola Sturgeon) asked her to ask the Supreme Court of the United Kingdom for an authoritative ruling, which she did. The Supreme Court heard the Lord Advocate’s arguments, the arguments of the Advocate General (the top legal officer for the United Kingdom) and arguments from the Scottish Government (intervening – meaning that they are not party to the case but are allowed to give their own arguments, independently of the Advocate General).

A Note about the Court

The Supreme Court replaced the House of Lords in 2009 as the highest judicial body for the United Kingdom but takes essentially the same form and conducts the same business. There are 12 judges and, by custom, there are two from Scotland (trained in Scots law which is distinct in many respects from English law, especially as regards private law) and one from Northern Ireland. Currently, the two Scottish judges hold the Presidency and Deputy Presidency. Attempts to increase the diversity of the judges of the Court have had limited success. Lady Rose is the only woman and person of colour on the Court. Nine of the 12 were privately educated at fee-paying schools (compared with 7% of the general population), and all but one of the 12 were educated at either Oxford or Cambridge.

Five judges will consider most cases, but sometimes seven will hear a case, and, exceptionally, nine will be called upon. The judges in the referendum case were Lord Reed, President (from Scotland); Lord Lloyd Jones (from Wales); Lord Sales and Lady Rose (from England); and Lord Stephens (from Northern Ireland).

The Case: Admissibility

The Lord Advocate asked the Supreme Court the following questions:

Does the provision of the proposed Scottish Independence Referendum Bill that provides that the question to be asked in a referendum would be ‘Should Scotland be an independent country?’ relate to reserved matters? In particular, does it relate to: (i) the Union of the Kingdoms of Scotland and England (paragraph 1(b) of Schedule 5); and/or (ii) the Parliament of the United Kingdom (paragraph 1(c) of Schedule 5)?[3]

On the first question, the Court held that they both could consider the case as a “devolution matter”[4]and that they should hear the case because it is not “hypothetical, academic or premature” but rather “has already arisen as a matter of practical importance.”[5] The pre-screening of all Bills before the Scottish Parliament by the Lord Advocate did not prevent the Supreme Court also reviewing their constitutional legality. The alternative, the Court explained, is that the Lord Advocate, a single individual whom the Court noted is “not infallible,” would have an unreviewable power to prevent a Bill going before the Scottish Parliament.[6] Furthermore, it was unreasonable, as in the present case, that the Lord Advocate might consider it possible that a Bill would be lawful without being able to express confidence in that position and therefore it was reasonable to ask the Supreme Court for its opinion.[7]

The Case: The Merits

The Scottish Government presented two arguments: first, that Parliament did have the power to authorise an independence referendum under the Scotland Act; and second, that even if the Scottish Parliament did not have the power under the Scotland Act, it had the power under international customary law which is part of the UK constitution.

The Court considered the first argument in some detail while considering the second rather briefly.

Under the Scotland Act, the Court concluded that the matter of an independence referendum was not within the power of the Scottish Parliament. This is because the Scotland Act reserves (prohibits the Scottish Parliament from passing legislation on) matters relating to “the Union of the Kingdoms of Scotland and England” and “the Parliament of the United Kingdom.”[8] The Lord Advocate had argued that since the referendum would only be advisory and not binding, it did not concern the Union or the sovereignty of Parliament but the Court rejected these arguments. The wording of the Act is quite clear, and it was too much of a stretch to interpret it narrowly to permit the Scottish Parliament to hold a referendum on independence.

Interestingly, both the Advocate General (for the United Kingdom) and the Court agreed that the referendum would have major political import. The Advocate General argued that even an:

advisory referendum… would place political pressure on the United Kingdom Government and Parliament to respect the result by agreeing to independence for Scotland. It would be difficult for the United Kingdom Parliament to ignore a decisive expression of public opinion. A “no” vote would also be political significant in its impact.[9]

The Court agreed, referring also to the 2014 Scottish independence referendum and the Brexit referendum of 2016 as examples where the referendum result was not self-executing (i.e., could not and did not change the status quo automatically but required implementation by the UK Government and UK Parliament).[10]

Even if it is not self-executing, and can in that sense be described as advisory, a lawfully held referendum is not merely an exercise in public consultation or a survey of public opinion. It is a democratic process held in accordance with the law which results in an expression of the view of the electorate on a specific issue of public policy on a particular occasion. Its importance is reflected, in the first place, in its official and formal character. Statutory authority is needed (and would be provided by the Bill) to set the date and the question, to define the franchise, to establish the campaign period and the spending rules, to lay down the voting rules, to direct the performance of the counting officers and registration officers whose function it is to conduct the referendum, and to authorise the expenditure of the public resources required. Statutory authority, and adherence to the statutory procedure, confer legitimacy upon the result.[11]

The Court’s review of the international law of self-determination was more succinct but no less predictable. First though, a word about customary law in the UK: under the British constitution, treaties agreed between the United Kingdom and other States do not automatically become part of UK law. They must be implemented (legally incorporated) in some way, e.g., by an Act of Parliament or a statutory instrument. That was done for the European Convention of Human Rights in the Human Rights Act 1998[12] but not for other human rights treaties, such as the International Covenant on Civil and Political Rights (ICCPR) and the International Covenant on Economic, Social and Cultural Rights (ICESCR), both of which are mentioned in passing in the judgment.[13] However, customary international law, which develops over time based on the practice of States and legal opinions of States is automatically part of law in the UK. This means that although the Court could consider the provisions of the ICCPR and ICESCR (both of which include the right to self-determination) when interpreting domestic law, they do not have to follow those treaties. However, the law on self-determination is part of customary law and therefore the Supreme Court can and must consider and apply it.

But what does the law of self-determination entail? First of all, it is the right of self-determination of Peoples. But “Peoples” is a term of quite specific meaning in international law; and in the context of self-determination, it applies to Colonial Peoples. The right of self-determination as a right to independence is enjoyed by peoples in colonies. Colonies are defined according to two main tests: first of all, the political community itself must be geographically remote from the political community that controls it (e.g., the former colonies of Kenya and Ghana had a right to independence) and that control was not entered into through a voluntary union.[14] Scotland fails on both tests. First of all, it is contiguous (joined onto the rest of the United Kingdom). Second – and more importantly – Scotland was not colonised by England and Wales. I will leave the historians to debate the motivations behind the Treaty of Union in 1706, but as a matter of law, it was a union voluntarily entered into by two Peoples. The governments of Scotland and England agreed to create a new State: Great Britain. Scotland was not colonised or taken over as a part of England. At the same time, the Parliaments of Scotland and England each passed an Act to abolish themselves and create a new legal entity: the Parliament of Great Britain.

Today, nearly all former colonies have become independent States, and secession (the breaking away to create a new State) is rare. However, there is another justification for independence, often called remedial secession. This applies when a political community (usually a minority) within a State is subjected to systematic and prolonged humanitarian abuses to such an extent that the State ultimately loses any moral authority to govern it. The Supreme Court referred to the 1998 Quebec opinion[15] of the Canadian Supreme Court which set out these two bases for independence (decolonisation and remedial secession), but it might also have considered more recent examples where a right to secession was upheld. These include South Sudan, formed in 2011 after years of mass, systematic human rights abuses of the South Sudanese under the authority of the Sudanese government and, more controversially, Kosovo in 2008, after years of abuse of the Kosovar minority by the Serbian government. On the latter case, the International Court of Justice also confirmed that these are the only two legal bases for independence in the absence of consent between the parties.

Remedial secession is available as a last resort, when human rights and democratic participation internally are denied. In the Kosovo advisory opinion, the International Court of Justice did not determine whether Kosovo was in fact independent but in two separate opinions, Judges Yusuf and Cançado Trindade, emphasised that remedial secession is an exceptional measure when all other attempts at upholding a minority’s human rights have failed. Judge Yusuf explained:

… a racially or ethnically distinct group within a State, even if it qualifies as a people for the purposes of self-determination, does not have the right to unilateral secession simply because it wishes to create its own separate State, though this might be the wish of the entire group.  The availability of such a general right in international law would reduce to naught the territorial sovereignty and integrity of States and would lead to interminable conflicts and chaos in international relations.[16]

However, in cases where the State denies the minority rights to take part in their own democratic governance, including through some form of devolved governance, a right to independence might arise:

Under such exceptional circumstances, the right of peoples to self-determination may support a claim to separate statehood.[17]

… if a State fails to comport itself in accordance with the principle of equal rights and self-determination of peoples, an exceptional situation may arise whereby the ethnically or racially distinct group denied internal self-determination may claim a right of external self-determination or separation from the State which could effectively put into question the State’s territorial unity and sovereignty.[18]

Judge Cançado Trindade further explains the moral basis for the right to independence in such extreme cases:

The basic lesson is clear: no State can use territory to destroy the population. Such atrocities amount to an absurd reversal of the ends of the State which was created and exists for human beings, and not vice-versa.[19]

Under contemporary jus gentium [the law of Peoples], no State can revoke the constitutionally-guaranteed autonomy of a “people” or a “population” to start then discriminating, torturing and killing innocent persons, or expelling them from their homes and practicing ethnic cleansing, – without bearing the consequences of its criminal actions or omissions. No State can, after perpetrating such heinous crimes, then invoke or pretend to avail itself of territorial integrity; the fact is that any State that acts this way ceases to behave like a State vis-à-vis the victimized population.[20]

While there are a wide range of opinions on Scottish devolution and independence or the equality between the nations within the United Kingdom, it cannot credibly be argued that the United Kingdom’s treatment of Scotland and the Scottish People comes close to the levels of abuse witnessed in South Sudan or Kosovo. Furthermore, the very fact of the Scottish Parliament facilitates so-called “internal self-determination” (autonomy or self-government) so that in most aspects of day to day life, elected representatives of the Scottish People pass laws to govern Scotland. The Scotland Act itself upholds the Scots’ right to self-determination.

A word of caution is apposite before rushing to claim that any People anywhere can declare independence on the basis of their will alone. The United Nations Charter is ultimately a peace treaty that is based fundamentally on the principle of sovereign equality and independence of States. Peace is ensured by the principle of territorial integrity of States – the non-negotiability of States’ external borders. In the 77 years since the Charter was agreed, the United Nations has chipped away at States’ sovereignty with the growing body of human rights law and environmental law. And this is no bad thing. But the price of peace is the inviolability of State frontiers. And when those frontiers are violated, as happened in Ukraine in 2014 and again in 2022, we have a war that not only threatens the security of millions of Ukrainian residents but threatens the entire architecture of international law.[21]

The creation of the United Kingdom was a voluntary union that requires both (all) parties to agree to its termination. Another essential principle of international law is pacta sunt servanda: treaties must be upheld. That includes the Treaty of Union. It is not in this respect analogous to a romantic relationship. And we should be very cautious before asserting that international law should allow groups to break away without mutual agreement.

What happens next?

While many Scottish supporters of independence are deeply disappointed by the ruling, the Scottish government cannot have been surprised as the law on this point is long settled.

How the Scottish and UK governments respond to the ruling is a matter for politicians. It is now beyond any doubt that a referendum requires the approval of the UK government to be lawful, as happened in 2013 for the 2014 vote. First Minister Sturgeon has long indicated her intention to campaign solely on independence at the forthcoming general election. The SNP can, of course, campaign on whatever it wants. However, it is worth returning to the arguments of the Advocate General, with which the Court agreed, that a referendum is not just a mere consultation exercise or public opinion survey: it has major political impact, and its results cannot be ignored by the losing party.

The clear expression of its wish either to remain within the United Kingdom or to pursue secession would strengthen or weaken the democratic legitimacy of the Union, depending on which view prevailed, and support or undermine the democratic credentials of the independence movement. It would consequently have important political consequences relating to the Union and the United Kingdom Parliament.[22]

[1] Scotland Act 1998, c. 46 (UK).
[2] Scotland Act, c.46 (UK), s31(1) and Scottish Ministerial Code, para 3.4.
[3] Reference by the Lord Advocate of devolution issues under paragraph 34 of Schedule 6 to the Scotland Act 1998 [2022] UKSC 31 (UK) (Judgement) para 12.
[4] Scotland Act, schedule 6, para 34.
[5] Judgment, paras 53-54.
[6] ibid, para 44.
[7] ibid.
[8] Scotland Act, s29(2)(b) and schedule 5, para 1(b) and (c). Judgment, paras 82-83.
[9] Judgment, para 62.
[10] ibid, para 79.
[11] ibid, para 78, see also para 81.
[12] c. 42 (UK).
[13] International Covenant on Civil and Political Rights, 16 December 1966, entered into force 23 March 1976, 999 UNTS 171; International Covenant on Economic, Social and Cultural Rights, 16 December 1966, entered into force 3 January 1966, 993 UNTS 3.
[14] UN General Assembly, Resolution 1514 (XV), Declaration on the granting of independence to colonial countries and peoples, 1960; UN General Assembly, Resolution 1541 (XV), Transmission of information under Article 73e of the Charter, December 15, 1960.
[15] Reference re Secession of Quebec [1998] 2 SCR 217 (CA).
[16] Accordance with International Law of the Unilateral Declaration of Independence in Respect of Kosovo (Request for Advisory Opinion), International Court of Justice Reports 2010, 403, Separate Opinion of Judge Yusuf, para 10.
[17] ibid, para 11.
[18] ibid, para 12.
[19] Accordance with International Law of the Unilateral Declaration of Independence in Respect of Kosovo (Request for Advisory Opinion), International Court of Justice Reports 2010, 403, Separate Opinion of Judge Cançado Trindade, para 176.
[20] ibid, para 206.
[21] Rachael Lorna Johnstone, “Why this War is Different,” The Polar Connection, March 10, 2022, (also considering Russian claims that they were upholding the “self-determination” of (some) Ukrainians).
[22] Judgment, para 81.

Rachael Lorna Johnstone is Professor of Law at the University of Akureyri and at Ilisimatusarfik (the University of Greenland).
Professor Johnstone specialises in Polar law: the governance of the Arctic and the Antarctic under international and domestic law. She has published widely on the rights of Indigenous Peoples, international human rights law, governance of extractive industries in the Arctic, international environmental law, state responsibility and due diligence, and Arctic strategies. Her books include Regulation of Extractive Industries: Community Engagement in the Arctic (Routledge 2020) with Anne Merrild Hansen, Arctic Governance in a Changing World (Rowman and Littlefield 2019) with Mary Durfee, and Offshore Oil and Gas Development in the Arctic under International Law: Risk and Responsibility (Brill 2015).
Professor Johnstone is an active member of the International Law Association and two thematic networks of the University of the Arctic: on Arctic Law and on Sustainable Resources and Social Responsibility. She is a member of the board of the Icelandic Human Rights Center. She is also a member of the Arctic Circle Mission Council on Greenland in the Arctic and serves on the advisory board of the Polar Research and Policy Initiative. She is the deputy member for Iceland on the Social and Human Working Group of the International Arctic Science Committee.
Professor Johnstone holds a doctorate in juridical science from the University of Toronto (2004), an M.A. in Polar Law from the University of Akureyri (2014), an LL.M. (magna cum laude) in Legal Theory from the European Academy of Legal Theory (2000) and an LL.B. (Hons) from the University of Glasgow (1999).

This Case Comment has been commissioned by Polar Research and Policy Initiative, with the support of the EMIF managed by the Calouste Gulbenkian Foundation. 

Disclaimer: The sole responsibility for any content supported by the European Media and Information Fund lies with the author(s) and it may not necessarily reflect the positions of the EMIF and the Fund Partners, the Calouste Gulbenkian Foundation and the European University Institute.
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