Introduction

A constitution is a set of rules and principles determining the way in which the political system itself operates. It creates the main institutions of government, and determines the way they are supposed to interact with each-other and with the public. Many countries internationally have a text setting out some of the main features of their constitution, often known as a ‘written’ or ‘codified’ constitution. The text typically has a special status, which is treated as being the ultimate source of legal authority within the society. Any law or action by a public authority that the courts find to be in conflict with the constitution can be ruled invalid. Changes to the constitutional text tend to be subject to meeting a heightened amendment procedure, such as the holding of a referendum (see: chapter 8) intended to ensure that they command a higher than normal level of consensus.

The UK does not have such a text, and is often described as having an ‘unwritten’ or ‘uncodified’ constitution. In fact, important parts of the constitution are written down, and various codes set out significant features of it; but the terms ‘unwritten’ or ‘uncodified’ convey that there is not a text specifically described as ‘the constitution’ and given exceptional legal status, as is the case in other countries. The rules and principles that might otherwise be found in a ‘written’ or ‘codified’ constitution are found in various different sources. They include Acts of Parliament; conventions (that is shared understandings about the way in which the system is supposed to function, that lack direct legal force); the ‘law and custom’ of the UK Parliament (meaning the rules according to which the UK Parliament functions); decisions made by the courts; and even views of what the constitution is as expressed by expert observers. Brexit was a significant occurrence from the perspective of this constitution.

Diving Deeper

Parliamentary sovereignty

When understanding the significance of Brexit to the UK constitution, it is important to appreciate a concept known as parliamentary sovereignty. Traditionally, the ultimate source of legal authority in the UK, rather than a constitutional text, is the UK Parliament. It – according to more orthodox theory – is able to make or unmake any law by passing an Act of the UK Parliament. It can change the UK constitution itself, even altering the rules that apply to Parliament itself, by largely the same procedure as Parliament would use for more regular legislation. This constitutional principle, sometimes known as the doctrine of parliamentary sovereignty, was promoted heavily by the constitutional lawyer, Albert Venn Dicey, from the late nineteenth century onwards, although it arguably has roots stretching back centuries earlier. Membership from 1973 onwards of what became the European Union (EU) raised difficult questions about the viability of this constitutional tenet. It meant, on some interpretations, that Parliament was no longer sovereign since it was subject to European law as produced by the organs of the EU (and its precursors). If a court found an Act of Parliament to be incompatible with EU law, it could disapply – that is, set aside – those parts of the Act that led to this violation. EU law was incorporated into UK law by Parliament itself through the European Communities Act 1972. Parliament could in theory repeal this Act if it chose, and ultimately it did so through the European Union (Withdrawal) Act 2018, paving the way for Brexit. But while the 1972 Act remained in force, it represented a limitation on Parliament, albeit self-imposed.

Parliamentary sovereignty and Brexit

Opponents of UK participation in European integration often objected to this project on the grounds that it entailed restricting the authority of Parliament and thereby compromising a core aspect of the UK constitution. When the goal of Brexit was achieved, from this point of view, parliamentary sovereignty was revived. In this sense, you might think that departure from the EU entailed the restoration of an earlier order. But in other respects, it generated significant uncertainties about the nature of the ‘unwritten’ or ‘uncodified’ UK constitution. Important changes had taken place in the period since 1973, that leaving the EU would not simply reverse. They included the rise of the referendum (see: chapter 8); an expanded role for the judiciary in reviewing the actions of public authorities (see: chapter 5); and the introduction of devolution to Wales, Scotland and Northern Ireland (see: chapter 11: it was a reintroduction in the case of Northern Ireland). Devolution for Northern Ireland was part of a peace process to which the absence of a hard border within the island of Ireland was integral (see: chapter 12).

Representative and direct democracy

The UK adopted a policy of leaving the EU following a referendum held on 23 June 2016 (see: chapter 8). On this occasion, on a turnout of 72.2 per cent, 51.9 per cent voted in favour of Brexit, 48.1 per cent in favour of remaining within the EU. This result had no legal force. But it had political weight. There might be said to be a convention that referendum results should be abided by, even though a compulsion to abide by them does not exist in law. A majority of members of the House of Commons and House of Lords, the two chambers of the UK Parliament, had supported a ‘remain’ outcome. But most of them accepted – in principle at least – that the vote in favour of departure from the EU was in practice binding upon them; as did successive UK governments up to the period of actual exit in January 2020. There were numerous disagreements about the precise way in which this decision should be implemented. Some politicians (and members of the public) held that the result need not be implemented, or that it should be subject to a further confirmatory referendum. But that a popular vote led to an outcome of such far reaching significance despite the lack of support at parliamentary level was arguably a constitutional event of immense importance. The UK constitution broadly speaking functions in accordance with principles of representative democracy, under which politicians who are accountable to the people take decisions on their behalf. The EU referendum and its aftermath implied that direct democracy – with voters pronouncing on specific issues – could override the representative principle.

The role of the judiciary

One argument offered in favour of Brexit was that it would shift decision-making away from courts interpreting European law and towards politicians. This transition, supporters of Brexit held, would be democratically beneficial. But in some ways the Brexit experience led to an expansion in the importance of the courts, at least in the short term, albeit interpreting UK law. Some of the disagreements that arose during the protracted period of controversy following the 2016 referendum were taken to the judiciary to resolve. Most famously, the Supreme Court reached decisions on the two Miller cases, respectively in 2017 and 2019. On both occasions, it found against the government of the day and, as the court presented it, upheld the rights of Parliament. On the first, the Supreme Court found that express approval was required in the form of an Act of Parliament before the UK could trigger Article 50 of the Treaty on European Union, commencing the process of departure. On the second, it ruled that an attempt by the government to prorogue Parliament in order, the court held, to prevent Parliament from performing its proper constitutional function of holding the government to account was unlawful. Both decisions generated intense controversy, both because they engaged with a highly divisive subject matter; and because they involved the judiciary becoming involved in matters which, some held, should be resolved politically and not in the courts (see: chapter 5). The Conservative government returned to power at the General Election of 2019 was committed to reviewing the role of the judiciary, on the grounds that it should not, as it saw it, encroach upon democratic processes. But whatever the outcome of this project, in the post-Brexit legal environment, the courts will have an important role in interpreting those aspects of EU law that have been retained in a UK context. They will in this sense, and others, continue to be involved in political matters.

The territorial constitution

Brexit has produced significant uncertainties in the territorial constitution of the UK. It raised complex questions about how powers transferred from EU to UK level would be exercised. Many of them fell in areas, such as agricultural policy, that were technically devolved to Wales, Scotland and Northern Ireland (see: chapter 11). Yet the UK government emphasised the importance of pursuing uniform approaches if the UK were to continue to be a single market. Disagreements arose over matters such as how much divergence between parts of the UK should be allowed; and how much of a role should be provided to the devolved institutions in determining decisions taken for the whole UK that impacted upon their areas of operation. The 2016 referendum saw significant variations in voting patterns across the UK. Scotland, Northern Ireland and London all produced ‘remain’ majorities, for instance. In this sense, Brexit was territorially divisive and intensified doubts about the future place of Scotland and Northern Ireland within the UK. The Brexit arrangement reached for Northern Ireland effectively included this territory of the UK within a separate regulatory and customs system to that of Great Britain, as a means of preserving the peace settlement for the territory (see: chapter 12).

A ‘written’ or ‘codified’ constitution

As discussed above, an important motive for the project of departure from the EU was the desire to remove restrictions on the UK Parliament in its ability to legislate in any way it saw fit. While the UK does not have a ‘written’ or ‘codified’ constitution, being a member of the EU in some ways provided a substitute for such a text. It meant that there was a higher set of rules that took precedence over all others. Some welcomed the removal of what they saw as an inappropriate external imposition. Others feared a potential for Parliament, driven by whichever group was dominant within the House of Commons and able to form a government, to abuse its enhanced power. They noted that the protection for individual freedom that the European Charter of Fundamental Rights had previously provided had been removed in the UK as a consequence of Brexit. Partly for these reasons, one constitutional commentator, Vernon Bogdanor, has argued that Brexit could provide a moment to seek to introduce a written constitution for the UK (Bogdanor: 2021).

Summary

Membership of the European Union and its precursors was challenging from the perspective of the doctrine of parliamentary sovereignty. The desire to protect or restore this doctrine was a motivation for some advocates of Brexit.

The UK differs from most other countries in that it does not have a ‘written’ or ‘codified’ constitution. EU membership in some senses provided some of the features of such a text. In particular it entailed limitations on the power of the UK Parliament – though these constraints applied within the UK system through an Act of Parliament.

Departure from the EU has raised a variety of constitutional uncertainties, around the future role of the courts, the relationship between direct and representative democracy, and the territorial constitution.

Brexit has also led some to suggest that, given the removal of an arguable restriction upon parliamentary sovereignty, it is time to consider introducing a ‘written’ or ‘codified’ UK constitution.

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