Stephen Tierney: The Lord Advocate’s Reference: Referendums and Constitutional Convention

On 11-12 October the Supreme Court is scheduled to hear a reference brought by the Lord Advocate under the Scotland Act 1998, Schedule 6, para.34 (‘the Reference’). The Lord Advocate seeks determination of 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 (para.1(b) of Schedule 5); and/or (ii) the Parliament of the United Kingdom (para.1(c) of Schedule 5)?

Section 29(1) of the 1998 Act provides that an Act of the Scottish Parliament is not law so far as any provision of the Act is outside the legislative competence of the Parliament. A provision is outside that competence so far as it “relates to reserved matters” (s.29(2)(b)), and whether or not it relates to a reserved matter is to be determined by “reference to the purpose of the provision, having regard (among other things) to its effect in all the circumstances” (s.29(3)).

The Lord Advocate contends that neither the draft Bill nor the referendum it proposes relate to the reserved matters of the Union or Parliament because the proposed referendum would be merely ‘advisory’, ‘consultative’ or ‘non-binding’ and hence would have no legal ‘effects’. In this post and another to follow I explore this claim.

Although the respective arguments of both the Lord Advocate and the Advocate General turn on whether the proposed referendum would be advisory’, ‘consultative’ or ‘non-binding’, neither submission explores this concept in detail. In this post I address the constitutional status of referendums within the UK constitution, suggesting that there are arguably a number of constitutional conventions attaching to referendums, including one concerning the implementation of a referendum’s outcome. As such it is difficult to argue that a referendum, even though having no automatic legal effects, does not have constitutional effects, thereby bringing a referendum on a reserved matter, even a referendum purporting to be advisory or non-binding, within the purview of s.29(3).

There are two senses within the constitution in which a referendum tends to be described as advisory or non-binding: where the referendum result is not itself self-executing, and at the level of high constitutional principle, where Parliament’s legislative supremacy remains unaffected by the process.

Key to the argument presented by the Lord Advocate is a distinction between a referendum that is ‘self-executing’ and one that is not. In other words, a referendum which would, under the parent statute, give automatic effect to legal change without the further intervention of Parliament. We see this distinction when we contrast the referendum on the electoral system in 2011 with the Brexit referendum in 2016. The Parliamentary Voting Systems and Constituencies Act 2011 s.8 required the Minister, in the event of a vote in favour of a new electoral system, to bring into force the provisions in the Act that would create such a system. In this way the referendum was an automatic trigger for legal change.

The Brexit referendum was different of course. The European Union Referendum Act 2015 was silent as to the consequences of a majority vote for Leave, and so the referendum result required for its implementation the passage of further legislation by Parliament, both to inform the European Commission of the UK’s intention to withdraw and to ratify the agreements with the EU that were eventually reached. 

The Supreme Court (Moohan, para 47) has also used the term ‘advisory’ to mean non-self-executing in relation to the referendum on Scottish independence in 2014. As the Lord Advocate observes, “unless Parliament makes specific provision to the contrary, rendering the referendum self-executing, any referendum has no effect in law” (Lord Advocate’s Written Submission, para 80).

There is a second sense in which referendums in the United Kingdom are taken to be advisory, consultative or non-binding. This stems from the fact that Parliament, as the supreme law-maker, is never bound in law either by an earlier statute or by a referendum authorised by such a statute. Therefore, even if an Act provides that a referendum result is self-executing, Parliament could, after the referendum takes place, change the law to provide that the result not be implemented. The House of Lords Constitution Committee’s 2010 report on Referendums in the United Kingdom (para 197) makes this point: “[B]ecause of the sovereignty of Parliament, referendums cannot be legally binding in the UK, and are therefore advisory.” The Supreme Court (para 7) also said of the Brexit referendum: “Technically, the result was not legally binding.”

These two points do not however fully account for the political or constitutional significance of a referendum within the United Kingdom constitution. Notably the Constitution Committee (para 197) qualified the comment quoted above, as follows: “However, it would be difficult for Parliament to ignore a decisive expression of public opinion.” The Supreme Court in Miller II (para 7) makes a similar point. Although technically the result was not legally binding, “the Government had pledged to honour the result and it has since been treated as politically and democratically binding. Successive Governments and Parliament have acted on that basis.”

These points of qualification recognise that a referendum result carries a constitutional significance that goes beyond any immediate effect it might have in law or its relationship to legislative supremacy. A referendum result may have a general effect within the constitution in terms of the political ramifications it will have. More concretely, it is also worth considering if there are now constitutional conventions attaching to referendums and their outcomes.

The UK Parliament website defines a referendum as follows: “A referendum is when a question is decided by putting it to a public vote. Referendums are an example of direct democracy. In the UK, most decisions are made by Parliament on behalf of the public which is known as indirect or representative democracy.” This recognises that a referendum within the British constitution is understood to be an alternative means by which the electorate directly is given a decisive role in relation to a particular issue. A significant set of functions remains for the legislature to perform: Parliament sets the date and the question, and establishes the process, franchise, campaign period, spending rules etc. for the referendum. It also has the authority to decide how the decision will be implemented. But the referendum vote itself is accepted as the determining factor in settling the substantive matter at issue.

On this basis a further register emerges upon which the ‘bindingness’ of referendum results should be assessed within the constitution: the implicit constitutional commitment between the legislature that organises and authorises the referendum on the one hand and the body of citizens mobilised to take part in the referendum on the other (for discussion of a related constituent power dimension to referendums see here).

Referendums in the UK are very rare events, organised by governments usually in extraordinary situations in order to arrive at a decisive position on an issue of public policy, often where the matter deeply divides both the country and political parties. Their potential significance was recognised even by Dicey, that firm advocate of Parliament’s supremacy, who declared “some decisions… must be referred to a more august tribunal than the House of Commons, or even than Parliament.” ((1894) 23 National Review 65 at 71)

UK-wide referendums have only been held on three occasions, each of these authorised by an Act of Parliament. It was well understood by those who voted, and indeed can reasonably be said to have been a condition upon which they participated, that whether or not the result was legally self-executing it would be politically binding, requiring Parliament to act upon the outcome. The Constitution Committee (para 6) commented on the Brexit referendum result:

The referendum result was clear. It will be the Government’s task to determine how the will of the people, expressed in binary terms in the referendum, should be implemented, and where among the range of potential outcomes the final settlement by which the UK leaves the EU will be made.

It is in this context that the Advocate General responds to the Lord Advocate’s argument that the proposed referendum would have no ‘effect’ on the Union. Discussing clause 1 of the proposed Bill, the Advocate General states:

That clause 1 describes the referendum as ‘ascertaining the views of the people of Scotland’ is of no assistance to the Lord Advocate. All electoral exercises concern the ascertainment of the views of the electorate, with referendums doing so with particular specificity.

(Advocate General’s Written Submission, para 73)

The Advocate General does not elaborate upon what it means to say that referendums have ‘particular specificity’ but his submission does state:

It is, of course, right that the outcome of the referendum provided for by the Draft Bill has no legal effect: it is not ‘self-executing’. But nor can it credibly be suggested that the outcome of the referendum will be ‘advisory’ in the sense of being treated as a matter of academic interest only: a referendum is not, and is not designed to be, an exercise in mere abstract opinion polling…  

(Advocate General’s Written Submission, para 78)

It can be argued convincingly that, following the two referendums which have been held on membership of the EC/EU and the effect given to these (in the latter case endorsed by a further general election result), there is now a constitutional convention to the effect that Parliament is expected to implement the outcome of any referendum which it authorises either directly, or indirectly through the devolution statutes. This is supported by a series of commitments made by Parliament in law either to implement the result of referendums, or to take no legislative action contrary to the outcome of a referendum – here, here and here.

It has also been argued by a Constitution Unit inquiry paper (para 88) that it is now the case that, where a referendum has been held on a particular matter, by convention a referendum would be expected to be used again in respect of the same issue. The House of Lords Constitution Committee has also stated (para 94):

[I]f referendums are to be used, they are most appropriately used in relation to fundamental constitutional issues… we would consider to fall within this definition any proposals… For any of the nations of the UK to secede from the Union.

Referendums have also only rarely been held at devolved level, and on each occasion, whether or not the referendum was self-executing (as the 1979 referendums were), Parliament has given effect to the outcome. This would appear to strengthen the argument that in respect of referendums held at both national and devolved levels there exists such a constitutional convention, imposing a conventional obligation upon Parliament to give effect to the result when it has no automatic legal effect. Furthermore, given that this convention, if it exists, relates to the democratic will of the people, it is arguable that it ought to be considered as a particularly important convention, analogous to those which attach to votes of no confidence in Parliament and the appointment of new governments. 

The Lord Advocate in her submission (para 122) states that: “Beyond the immediate effect of ascertaining the will of the people of Scotland, the practical effects of an advisory referendum are speculative. The court ought not to engage in such speculation because it is not equipped to do so.” She continues (para 123): “Furthermore, it would also not be constitutionally appropriate for this Court to take into account the possibility of future legislation of the UK Parliament.”

The Lord Advocate is correct that the vague language of s.29(3) leaves scope for various arguments about competence. When the referendum is placed in the context of established UK constitutional practice however the practical effects of a referendum are arguably less speculative. And while a court cannot take into account what future legislation might say, it can recognise that there exists a constitutional obligation to give effect to a referendum outcome. If such an obligation exists then it could well be viewed as an ‘effect in all the circumstances’ for the purposes of s.29(3). And if it is taken to have a constitutional effect through established practice or convention, even in the absence of self-executing legal effects, then it would, in light of the Supreme Court’s interpretation of s.29(3), most likely be taken to ‘relate to’ the Union or to the Parliament of the United Kingdom and therefore to fall beyond the competence of the devolved institutions.

Stephen Tierney is Professor of Constitutional Theory at the University of Edinburgh and author of Constitutional Referendums: The Theory and Practice of Republican Deliberation. He also serves as Legal Adviser to the House of Lords Select Committee on the Constitution.

This post is written in a personal capacity. I am grateful to Mike Gordon and Alison Young for helpful comments.

(Suggested citation: S. Tierney, ‘The Lord Advocate’s Reference: Referendums and Constitutional Convention’, U.K. Const. L. Blog (4th October 2022) (available at