Brexit has led to numerous clashes between London and the devolved governments, raising fundamental questions about the very nature of the United Kingdom, in a context where the European Union is no longer available as an ‘external support system’. Michael Keating argues that we need to find new constitutional concepts for living together in a world in which traditional ideas of national sovereignty have lost their relevance.

Since the Brexit vote, there have been repeated clashes between the UK and devolved governments. Some of these concern policy differences, notably over the form Brexit should take. Some reflect the inadequacies of mechanisms for intergovernmental relations. There is an inevitable rivalry between political parties at different levels. Beneath all this, however, are fundamental questions about the nature of the United Kingdom as a polity and where ultimate authority lies, especially after 20 years of devolution.

On the one hand, there is the classic or ‘Westminster’ doctrine, according to which sovereignty resides with the Monarch-in-Parliament. In the absence of a written, codified and enforceable constitution, this is the only foundation of authority. In this view, Westminster has merely ‘lent’ competences to the devolved legislatures, which can be taken back at any time, however politically imprudent that might be. Westminster may not often exercise this power but it provides a trump card in any conflict with the devolved authorities.

This is a powerful doctrine but at the same time an empty one since it rests on a tautology. Westminster is sovereign because, by dint of its sovereign authority, it says it is. The point was illustrated in the debates on the 1978 devolution legislation when an alliance of unionists and nationalists defeated a clause asserting that Westminster remained supreme, the nationalists because they did not want it to be true and the unionists because it was redundant. Westminster sovereignty is a myth, that is a story that may be true or false but works as long as people believe it. When the spell is broken, as it has in recent years, its supporters have to fall back on other arguments. There is a historical argument, that parliamentary sovereignty is rooted in constitutional practice; a normative argument, that in an age of universal suffrage, it really amounts to popular sovereignty; and an instrumental argument, that it allows for powerful and effective government. All are open to question. The historical argument is based on English practice and challenged in Scotland. The normative argument assumes that there is a single UK people with one channel for expression, rather than multiple peoples, the smaller nations having more inclusive electoral systems. The instrumental argument needs to be proven empirically rather than asserted.

Standing against the Westminster doctrine is a tradition of constitutionalism based on a wider epistemic reasoning. Rather than all authority as stemming from one place, there are multiple sources of legitimate authority. Constitutional reasoning cannot be reduced to a simple fiat but must take into account multiple historical accounts, precedent, convention and interpretations of the democratic principle. They may also see the UK itself not as a unitary state (a phrase still used in Government documents) but as a plurinational union . This involves a reading of history as one of contested sovereignties but also a recognition that devolution in 1999 represented a constitutional transformation rather than a mere reassignment of functions in a unitary state.

Academic lawyers, political scientists and even judges (speaking obiter dicta or in lectures) have frequently raised these questions, arguing that devolution, human rights legislation and (in its time) membership of the European Union, have called the traditional doctrine of Westminster sovereignty into question. Westminster itself has made some moves such as incorporating in the Scotland and Wales Acts clauses stipulating the devolved parliaments can be abolished only by referendum in the respective nations. Yet nothing stops it repealing these clauses themselves.

Nor have judges challenged parliamentary supremacy when making actual decisions. The Supreme Court, which might have engaged in wider constitutional reasoning, has strictly enforced the Westminster doctrine, notably when it pronounced that the legislative consent convention (also known as the Sewel convention, whereby Westminster does not ‘normally’ legislate in devolved matters without the consent of the relevant devolved legislature) was merely political. This contrasts with the Supreme Court of Canada, which has in recent years interpreted Canada’s written constitution in an expansive way to encompass principles like federalism and democracy as well as the letter of the law.

Since devolution (and arguably since the 1707 Acts of Union), the United Kingdom has lived with these competing interpretations of the constitution. Foundational issues about sovereignty have been left in abeyance, which may be the best way to deal with fundamental disagreements as long as the practical business of government is not affected. It is not uncommon, especially in plurinational states like the UK, Canada or Spain. The Northern Ireland settlement was, for good reasons, designed precisely to suspend the arguments of principle until such time as consensus might be reached. The current experience of Spain and Catalonia shows the dangers when matters of sovereignty become absolutes and claims are pushed to the limits by both sides.

Brexit, however, has forced the issue. It was predicated on restoring sovereignty to a putative unitary and sovereign parliament. Although that rapidly mutated into the sovereign will of the people, expressed in the Brexit referendum, that makes the problem even more acute as it assumes the existence of a single British people or demos. The contrasting votes in England and Wales, in Scotland and in Northern Ireland (and within Northern Ireland, between British and Irish identifiers) put this issue to the fore. Brexit was based on an argument that shared sovereignty in the EU was incompatible with British constitutional practice. Taking the alternative view on the UK constitution, however, there is a deep affinity between the United Kingdom and the European Union. Both are plurinational unions in which issues of demos (who are the people), telos (the purpose of the union), ethos (the extent of shared values) and sovereignty are contested and never resolved but continually negotiated. This is one way in which the EU provided an external support system for UK devolution – other effects included the opening of the border between the two parts of Ireland and the European Single Market, which obviated the need for strict internal market provisions within the UK itself.

Constitutional reformers have long called for a codified, written constitution to resolve these issues. This has been accompanied by calls for a constitutional convention or citizen’s assembly to put the power back into the hands of the people. Such democratising moves have obvious merits but often fail to distinguish between two types of constitution. One type is based on a unitary people, or demos, and expresses unity of purpose and destiny. The other type is where foundational consensus is lacking and the constitution must encompass differing views of demos, telos and sovereignty; Northern Ireland is an extreme example. There may come a moment at which a British people is ready to express its fundamental unity, whether through a unitary state or a symmetrical federation. Alternatively, it may break up into its constituent parts. In the meantime, constitutionalism will remain a matter of accommodating different aspirations while respecting shared principles of democracy, diversity and subsidiarity.

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About the author

Michael Keating is Professor of Politics at the University of Aberdeen. The arguments here are drawn from his book State and Nation in the United Kingdom: The Fractured Union, Oxford University Press, 2021.