Pravar Petkar: Consultative Referendums and Constituent Power in the UK

On 28 June 2022, the Scottish First Minister announced that the Lord Advocate had made a reference to the UK Supreme Court on whether a Bill for a consultative referendum on Scottish independence would fall within the Scottish Parliament’s legislative competence. Although there has already been much discussion  on the issue of legislative competence (see herehere and here), this post argues that consultative referendums have a broader constitutional significance that might impact both the determination of competence and the steps that will follow the court’s ruling.

Consultative and determinative referendums

Consultative referendums do not have direct legal consequences. Notable examples in the UK include the 2014 referendum on Scottish independence and the 2016 Brexit referendum. In both cases, the enabling statute for the referendum was silent as to the consequences of the result. Consultative referendums are contrasted with binding or ‘determinative’ referendums (as Tierneyterms them) in which the result automatically comes into effect in law or produces other legal consequences. For example, there was a statutory obligation for provisions for Alternative Voting (AV) to be brought into effect by the relevant Minister had the 2011 referendum on the matter in the UK produced a majority in favour of AV. The Scottish Government’s choice of a consultative referendum, as in 2014, is therefore significant, as it is not expected to generate legal issues beyond that of the competence to hold it. As clause 1 of the yet-to-be-introduced Scottish Independence Referendum Bill states, the referendum is “ascertaining the views of the people of Scotland on whether Scotland should be an independent country.” It is not to immediately effect Scotland’s independence from the UK in the event of a majority vote.  

Does the distinction hold in the UK?

This distinction, nevertheless, is not particularly helpful in the UK because of the doctrine of parliamentary supremacy. In Dicey’s traditional account, the Westminster Parliament has unlimited legislative competence and cannot be bound by any other institution, whilst the contemporary ‘manner and form’ understanding suggests that Parliament can bind itself as to certain procedural matters. Given this, consultative referendums appear to be purely consultative: whilst the result may inform legislators, it is legally open for the Westminster Parliament to diverge from it if it so chooses. Although determinative referendums do produce some immediate legal consequences, parliamentary supremacy, as Gordon has suggested, entails that they too are in some sense advisory: where, as in the Parliamentary Voting System and Constituencies Act 2011 or the Scotland Act 1978, the enabling statute contains a duty to implement the result, Parliament could simply repeal that statutory duty. This is because no positive law can permanently bind Parliament; Parliament is only so bound until and unless it repeals the relevant law. Given this, a full consideration of the constitutional effects and significance of referendums in the UK must look beyond positive law to the political constitution. 

Referendums and the tube of toothpaste

‘Once the toothpaste has been squeezed out of the tube, you can’t put it back in’. This popular English metaphor is an injunction to be careful with our words – once something is said, it cannot be taken back – but equally applies to the non-legal effects of referendums in the UK. The direct or semi-direct form of democracy encapsulated by the referendum runs in stark contrast to the strong emphasis on representative democracy in the UK constitution. On the traditional Burkean model, those elected by the people to sit in the Commons are representatives of the ‘nation’ and are crucially free to exercise their own judgement on policy without being bound by instructions from their constituents. This suggests that referendums cannot neatly dovetail with the representative system by specifying the “political mandate” of elected representatives, as Accetti and Oskian have suggested. Referendums in the UK, whether of the consultative or determinative variety, are better viewed according to the toothpaste metaphor: once the people have voted on an issue in a referendum, it is difficult to subordinate the force of that outcome to the views of elected representatives, as Young notes was the case with the 2016 referendum. The direct expression of popular opinion that comes from a referendum is thus the toothpaste that cannot be pushed back into the representative democratic tube, but instead hangs in the space of the political constitution, awaiting resolution.

Constituent power

If the referendum does act in this manner, how do we explain its significance in constitutional terms? It is contended that the enduring force of the referendum result outside the representative system can be conceptualised as an expression of constituent power. It is now widely recognised that constituent power is relevant not only at the founding of the constitutional order, but within it: the latter has been described as ‘derived’ constituent power and “constitutional constituent authority” amongst other formulations, denoting the presence of the constituent subject (the ‘nation’, ‘people’ or founding territories) within the constituted order. McHarg indeed suggested, in the wake of the 2014 independence referendum, that the very presence of the referendum within the independence process appears to introduce the question of the location of constituent power into the constitutional theory of the UK. Consultative referendums nevertheless have a relatively weak claim to constituent power as they reduce “the meaningfulness of what the people can be said to have consented to”. In a similar vein, Colon-Rios argues that whilst referendums that change the material constitution express constituent power, they do so imperfectly: constituent power is framed in normative terms as requiring a deliberative, participatory and inclusive process. Referendums therefore express a constituent power that operates outside – and perhaps in opposition to – the representative system and the related concept of parliamentary supremacy in the UK, although the extent of the strength of the constituent power will vary according to the nature and framework of the referendum in question. 

Although constituent power does not have legal consequences in the UK of the kind that Colon-Rios notes apply in various jurisdictions in Latin America, it nevertheless has non-legal constitutional significance. Loughlin and Tierney note that sovereignty extends beyond the legalistic idea of parliamentary supremacy to a “political-constitutional principle” which draws on principles of legitimacy and authority. The exercise of the state’s sovereign powers is, as a result, conditioned not only by the legitimacy of the principal organs of government but by legitimacy claims that arise outside the constituted powers. In other words, the legitimacy claims that stem from consultative referendums can impose practical restrictions on the exercise of the Westminster Parliament’s legislative powers. 

What does this mean in practice?

Various practical consequences might flow from this analysis, depending on whether the UK Supreme Court considers these issues in the reference. On one hand, as Torrance suggests, the court might regard the non-legal effects of the referendum as irrelevant. Should it then find the Bill within competence, a vote in favour of independence is likely to generate significant pressure on the UK Government to comply with the result. Whilst the referendum might not be binding in law, it might be seen as binding in practice by those who favour independence. Should the Bill be outside competence, then the First Minister has proposed to make the next Scottish Parliament election a de facto independence referendum. Such a vote, entailing the election of representatives rather than a direct vote on a policy matter, is less participatory than a referendum and so is better viewed as an election for the Scottish constituted powers rather than an expression of constituent power. This will be especially so if other Scottish parties make manifesto commitments on other policy issues, diluting the extent to which the election concerns a matter of constitutional change. On the other hand, the UK Supreme Court’s discussion of practical restrictions on the Westminster Parliament’s legislative capacity in the UNCRC Reference case in relation to ‘incompatibility declarators’ could be applied by analogy to a consultative referendum on independence held without a Section 30 Order. This would amount to a practical restriction on Parliament not generated by Parliament, qualifying parliamentary supremacy, and modifying s28(7) of the Scotland Act 1998, which “preserves the unqualified power of [the Westminster] Parliament to make laws for Scotland.” (§21).


The UK Supreme Court’s determination of the competence of the Scottish Parliament to legislate for a consultative referendum on independence will have profound constitutional significance. The constitutional issues raised by consultative referendums may appear before the court and tell against the Scottish Parliament’s competence in this matter because of the practical restrictions they impose on the Westminster Parliament’s ability to legislate. Nevertheless, even if the Bill is outside competence, an analysis based on constituent power exposes additional constitutional issues which call into question whether consultative referendums truly are ‘merely advisory’.

With many thanks to Professor Alison Young and Professor Michael Gordon for their extremely helpful comments and suggestions on a previous version of this post. Any remaining errors or inconsistencies are my own.

Pravar Petkar is a PhD Candidate at the University of Edinburgh Law School.

(Suggested citation: P. Petkar, ‘Consultative Referendums and Constituent Power in the UK’, U.K. Const. L. Blog (5th July 2022) (available at