Introduction
Defining the term 'constitution' is a foundational task in the study of public law. At its most basic, a constitution is the system of rules, principles, and practices that establish the primary institutions of the state, defining their powers and regulating the relationship between them, as well as the relationship between the state and its citizens. While this definition provides a starting point, the concept is multifaceted, as constitutions vary significantly in their form and substance across different nations. There is no single universal model. This essay will explain what a constitution is by first outlining its principal functions and then examining the main classifications used to categorise different constitutional arrangements. Throughout this discussion, particular reference will be made to the distinctive nature of the United Kingdom’s constitution to illustrate these concepts.
The Functions of a Constitution
To understand what a constitution is, it is essential to consider what it does. Broadly, a constitution performs several key functions that are fundamental to the operation of a state.
First, a constitution creates and defines the main organs of government. Typically, these are the legislature, the executive, and the judiciary. The constitution establishes their existence, composition, and core responsibilities. In the United Kingdom, for example, the constitution provides for a legislature (Parliament, comprising the House of Commons and the House of Lords), an executive (the government, led by the Prime Minister and Cabinet), and a judiciary (the court system, headed by the Supreme Court). Key statutes like the Parliament Acts 1911 and 1949, which regulate the relationship between the two Houses of Parliament, and the Constitutional Reform Act 2005, which established the Supreme Court, are part of this framework (Loveland, 2021).
Second, a constitution distributes and limits the power of the state. It allocates specific powers to each branch of government and, importantly, seeks to prevent the over-concentration of power in any single institution. This is often achieved through the doctrine of the separation of powers, a concept famously articulated by Montesquieu, which advocates for a clear division between the legislative, executive, and judicial functions (Montesquieu, 1748). While the US Constitution provides a classic example of this separation, the UK system is often described as having a 'fusion of powers' (Bagehot, 1867). This is because government ministers in the executive are also members of the legislature. However, principles such as judicial independence and parliamentary scrutiny serve as important 'checks and balances' to restrain government power.
Third, a constitution regulates the relationship between the different institutions of the state. It provides the mechanisms through which the branches of government interact. For instance, in the UK, constitutional conventions dictate that the Prime Minister must be a member of the House of Commons and that the government is accountable to Parliament through procedures like Prime Minister’s Questions and select committee oversight. The courts also play a role through judicial review, where they can scrutinise the legality of executive actions, as seen in the landmark case of R (Miller) v The Prime Minister [2019] UKSC 41, which affirmed the role of Parliament in the constitutional order.
Finally, a constitution defines the relationship between the state and the individual. It sets out the rights and freedoms of citizens and places corresponding limits on the state's power to interfere with them. In many countries, this takes the form of an entrenched Bill of Rights. In the UK, citizens' rights are protected through various sources, including common law and statutes such as the Human Rights Act 1998, which incorporated the European Convention on Human Rights into domestic law (Barnett, 2021).
Classifying Constitutions
The functions of a constitution are performed through different structural arrangements. Political scientists and legal scholars classify constitutions along several key axes, which helps to further refine our understanding of the concept.
The most common distinction is between a 'written' and an 'unwritten' constitution. A written, or codified, constitution is one where the fundamental rules and principles are contained within a single, authoritative legal document. The Constitution of the United States is a prime example. An unwritten, or uncodified, constitution, by contrast, is one where the rules are derived from a variety of sources. The UK constitution is the foremost example of this type. Its sources are diverse and include:
- Statutes of constitutional significance: These are Acts of Parliament that shape the state's structure and powers, such as Magna Carta 1215, the Bill of Rights 1689, the Acts of Union 1707, and the devolution legislation for Scotland, Wales, and Northern Ireland.
- Common Law: Judicial decisions have established key constitutional principles, including the rule of law and the extent of the Royal Prerogative (the executive’s residual powers).
- Constitutional Conventions: These are non-legal but politically binding rules of behaviour, such as the convention that the Monarch will grant Royal Assent to any bill passed by Parliament. As A.V. Dicey noted, conventions regulate the conduct of those in power (Dicey, 1885).
- Authoritative Works: The writings of constitutional experts like Walter Bagehot and A.V. Dicey are considered persuasive guides to understanding the constitution’s workings.
A second classification is between 'rigid' and 'flexible' constitutions. This relates to the process of amendment. A rigid constitution is one that is difficult to change, typically requiring a special procedure such as a supermajority vote in the legislature or a referendum. This entrenchment gives it a higher legal status than ordinary law. A flexible constitution, on the other hand, can be amended through the normal legislative process. Because the UK Parliament is sovereign, it can create or repeal any law, including laws of constitutional importance, with a simple majority. This makes the UK constitution highly flexible (Bradley et al., 2022).
Finally, constitutions can be classified as 'unitary' or 'federal'. In a unitary state, such as the UK, ultimate legal authority is concentrated in a central government. While power has been devolved to administrations in Scotland, Wales, and Northern Ireland, this devolution is not constitutionally guaranteed and, in theory, the Westminster Parliament could reclaim those powers. In a federal state, such as Germany or the United States, sovereignty is constitutionally divided between a central federal government and regional state governments, with neither being subordinate to the other.
Conclusion
In conclusion, a constitution is far more than a single document; it is the entire system of governance that establishes, empowers, and constrains the state. Its core functions are to create the organs of government, distribute power between them, regulate their interactions, and define the rights of individuals. As the classifications show, these functions can be achieved in different ways. Some constitutions are codified in a single document, rigid, and federal, while others, like that of the United Kingdom, are uncodified, flexible, and unitary. Despite its unusual form, drawing from statutes, common law, and conventions, the UK constitution effectively performs the fundamental roles expected of any constitutional system. Therefore, to ask "what is a constitution?" is to ask how a state is formally structured and how its power is ultimately controlled.
References
Bagehot, W. (1867) The English Constitution. Chapman and Hall.
Barnett, H. (2021) Constitutional and Administrative Law. 14th edn. Routledge.
Bradley, A. W., Ewing, K. D. and Knight, C. J. S. (2022) Constitutional and Administrative Law. 18th edn. Pearson.
Dicey, A. V. (1885) An Introduction to the Study of the Law of the Constitution. Macmillan.
Loveland, I. (2021) Constitutional Law, Administrative Law, and Human Rights: A Critical Introduction. 9th edn. Oxford University Press.
Montesquieu, C. de S. (1748) The Spirit of the Laws.
R (Miller) v The Prime Minister [2019] UKSC 41.
