Introduction to the UK constitution - Sources of constitutio...

Learning Outcomes

This article outlines the principal sources of the UK constitution and their operation in constitutional governance, including:

• The legal status, hierarchy, and relative authority of key constitutional sources, and how to prioritise them when they conflict in problem questions
• The interaction between statutes, common law, judicial precedent, constitutional conventions, the royal prerogative, and retained EU law when determining the validity of government action
• The practical application of constitutional statutes in defining, conferring, and controlling public powers exercised by Parliament, ministers, and public bodies
• The role of common law and judicial precedent in articulating constitutional principles such as the rule of law, residual liberty, and access to the courts
• The nature, operation, and constitutional significance of conventions, together with their limits as non-legal rules and their recognition by the courts
• The scope, control, and constitutional position of the royal prerogative, including its relationship with statute and judicial review
• The post-Brexit legacy, classification, and status of retained EU law, and its remaining interaction with domestic primary and secondary legislation
• The ways in which these sources collectively shape the structure of UK government, separation of powers, and the protection of individual rights and remedies
• The application of these principles to SQE1-style scenarios involving authority to act, conflicts between sources, and challenges to the legality of government decisions

SQE1 Syllabus

For SQE1, you are required to understand the principal sources of the UK constitution and their operation in constitutional governance, with a focus on the following syllabus points:

• the main sources of the UK constitution: statutes (Acts of Parliament), common law (case law), judicial precedent, constitutional conventions, royal prerogative, and retained EU law
• the legal status, authority, and hierarchy of each source
• the principle of parliamentary sovereignty and effects on the supremacy of statutes over other sources
• the development of constitutional principles through judicial decisions, including the doctrine of precedent and concepts such as rule of law and residual liberty
• the existence, nature, and operation of constitutional conventions (including their flexibility and political, non-legal, enforcement)
• the content and constitutional role of the royal prerogative
• the effect of devolution and the legislative competence of devolved parliaments
• the post-Brexit framework for retained EU law, its legal status, and how it relates to domestic law

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. Which source of constitutional law is considered the most authoritative in the UK?
2. What is a constitutional convention, and is it legally enforceable?
3. How does retained EU law continue to affect UK law after Brexit?
4. Give an example of a key constitutional statute and briefly explain its significance.

Introduction

The constitution of the United Kingdom is unique, distinguished by its lack of a single codified document and composed instead of multiple interlocking sources. These include legally binding sources—primarily Acts of Parliament (statute), supplemented by common law developed by judicial decision-making (including the role of judicial precedent), as well as certain non-legal but politically critical sources such as constitutional conventions. Understanding the status, scope, and application of these sources is essential when analysing government power, individual rights, and the relationships among Parliament, the executive, and the judiciary.

Key Term: constitution
The system of government and the rules—both legal and non-legal—that establish and regulate it. In the UK, the constitution is uncodified: it is not contained in a single document and draws from diverse sources.

Statutes: The Primary Source of Constitutional Law

Acts of Parliament are the most authoritative source of constitutional law in the UK. This reflects the doctrine of parliamentary sovereignty, under which the UK Parliament is the supreme law-making body. Statute law can be enacted or repealed by Parliament and, importantly, overrides all other domestic sources of law whenever a conflict arises.

Key Term: statute
A law formally enacted by the UK Parliament. Statutes (Acts of Parliament) are primary legislation and have the highest legal authority among domestic sources.

Many essential aspects of the constitution are set out in statutes, although there is no hierarchy which renders any one Act immune from repeal or amendment by a subsequent Act. Nevertheless, some statutes are recognised as having “constitutional” status due to their significant nature and subject matter. Examples of landmark constitutional statutes include:

• Magna Carta 1215: Widely regarded as a significant source of constitutional rights and liberties. Although most of its clauses are now obsolete, it established the principle that not even the monarch is above the law.
• Bill of Rights 1689: Restricted the power of the Crown, set out the rights of Parliament, prohibited suspending or dispensing with laws without parliamentary consent, and confirmed regular parliamentary sessions.
• Acts of Union 1707 and 1800: United England and Scotland (later incorporating Ireland) under a single Parliament, altering the constitutional architecture of the UK.
• Parliament Acts 1911 and 1949: Reduced the power of the House of Lords, establishing the supremacy of the House of Commons in most legislative matters and ensuring that the elected chamber’s will prevails where the Lords withhold consent.
• Human Rights Act 1998: Gave legal force in UK law to the rights protected under the European Convention on Human Rights, requiring all public authorities, including the courts, to act compatibly with those rights as far as possible.
• Constitutional Reform Act 2005: Reformulated the office of Lord Chancellor, created the Supreme Court, and strengthened the independence of the judiciary from the legislature and executive.
• Devolution Statutes – Scotland Act 1998 and 2016, Government of Wales Act 1998 and 2017, Northern Ireland Act 1998: Established devolved legislatures, delegating legislative powers on defined matters, but affirming that the supremacy of the UK Parliament survives.

Despite their importance, even constitutional statutes may be amended or repealed by ordinary legislative process. The courts have suggested, however, that constitutional statutes cannot be impliedly repealed and may only be repealed by express words (see Thoburn v Sunderland City Council [2002]).

Parliamentary Sovereignty and Statutes

The doctrine of parliamentary sovereignty—a central concept of the UK constitution—was classically formulated by Dicey as the right of Parliament to make or unmake any law whatever, and that no body or person (including the courts) can override or set aside Parliament’s legislation. The courts have consistently upheld the principle that they cannot question the validity of an Act, nor investigate the procedures by which it was passed (as affirmed in Pickin v British Railways Board [1974]). This remains true even where an Act conflicts with significant rights or international law; it is for Parliament to change the law, not the courts.

Key Term: supremacy of statutes
Where a statute conflicts with any other source of law, including the common law or royal prerogative, the statute prevails due to the principle of parliamentary sovereignty.

Worked Example 1.1

A new Act of Parliament is passed that conflicts with a long-standing common law rule. Which source of law prevails?

Answer:
The Act of Parliament prevails. Statutes override common law rules in the UK.

Statutory law is also the source of the majority of legal powers exercised by the executive and administrative authorities, including powers to make delegated (secondary) legislation—rules, orders, and regulations made under statutory authority.

Constitutional Statutes and Express/Implied Repeal

Some statutes are so significant to the framework of governance or to the relationship between the citizen and the state that they are described as “constitutional statutes.” Courts have suggested that constitutional statutes are immune from implied repeal (where a later statute conflicts with an earlier one without explicit language), but still may be expressly repealed by subsequent Acts of Parliament. Examples include the Magna Carta, the Bill of Rights 1689, the Human Rights Act 1998, the European Communities Act 1972 (while in force), and the Scotland Act 1998.

Common Law: Judicial Decisions and Constitutional Principles

In addition to statutes, the UK constitution is supported and shaped by the common law—a body of doctrine developed by judicial decisions over time. The common law establishes constitutional principles, fills gaps in statutory law, and, where Parliament is silent or ambiguous, continues to develop the overall framework of rights, liberties, and checks on power.

Key Term: common law
The body of law created and refined through judicial decisions, particularly those of senior appellate courts. Also called case law; it operates alongside and is subject to statute.

Notable constitutional principles established through the common law include:

• The rule of law—all persons (including state bodies and officials) are subject to the law, and there is no legitimate executive action without legal authority (Entick v Carrington [1765]).
• Judicial review—the judiciary’s power to review executive and administrative action for legality, ensuring public bodies act within their lawful authority.
• Residual liberty—individuals are free to do anything not expressly prohibited by law.
• Equality before the law—no individual, including ministers and officials, is above the law (M v Home Office [1994]).
• Access to the courts—a significant right supporting the constitutional order, important for the enforcement of rights and review of power.

Common law also provides presumptions when interpreting statutes, for example, the assumption that Parliament does not intend to infringe significant rights or access to the courts unless it uses clear and express words.

Key Term: judicial precedent
The system by which legal principles established in previous cases by higher courts are binding on lower courts when the material facts are similar. This ensures certainty and consistency in the law.

The Doctrine of Precedent

Judicial precedent is central to the development and coherence of the common law. The principle of stare decisis—to stand by that which has been decided—requires courts to follow the decisions of higher courts (vertical precedent) and, in some circumstances, their own earlier decisions (horizontal precedent). The Supreme Court is generally bound by its own decisions but may depart when it appears “right to do so.” The Court of Appeal is bound by its previous decisions except in certain situations (as outlined in Young v Bristol Aeroplane Co Ltd [1944]).

Precedent ensures that legal principles are applied consistently over time, but the doctrine is sufficiently flexible—higher courts can overrule past decisions, and courts may distinguish cases on their facts where appropriate.

Key Term: rule of law
The principle that government and individuals are all equally subject to law that is publicly made, clear, and applied by independent courts. The rule of law requires the exercise of state power to be justified by legal authority and constrains arbitrary action.

Worked Example 1.2

A government department acts without clear statutory authority. Can its actions be challenged?

Answer:
Yes. Under common law, public bodies must have legal authority for their actions. If not, their actions can be challenged in court.

Worked Example 1.3

A lower court is presented with binding precedent from a superior court on the same point of law. What is the effect?

Answer:
The lower court is required to follow the legal principle established by the superior court (vertical stare decisis), promoting consistent and predictable decision-making.

Constitutional Conventions: The Unwritten Rules

A distinctive feature of the UK constitution is the importance of constitutional conventions—established non-legal rules that govern political practice. Conventions regulate the relationship between the main organs of state (the executive, Parliament, and the Crown), filling gaps not settled by law and allowing flexibility and adjustment as political needs change. However, they are not legally enforceable: if breached, the courts will recognise their existence, but will not compel compliance.

Key Term: constitutional convention
A non-legal rule or established practice which is followed by the country’s political actors and institutions but is not legally enforceable or justiciable by the courts.

Common examples include:

• The monarch gives Royal Assent to all Bills passed by Parliament (the last refusal being in 1708).
• The Prime Minister must be a member of the House of Commons.
• Ministers are collectively responsible to Parliament and individually responsible for their departmental actions or personal conduct (the Ministerial code).
• The government will resign if it loses a vote of confidence in the House of Commons.
• The Sewel Convention: the UK Parliament “will not normally” legislate on devolved matters without the consent of the relevant devolved assembly (now given statutory recognition, but still regarded as politically, not legally, binding).

Key Term: ministerial responsibility
The convention that government ministers are accountable to Parliament for the conduct of their department and their personal actions.

Conventions are enforced by political pressure, public opinion, or, in extreme cases, dismissal from office, not by courts. Conventions’ flexibility is both their strength—allowing the constitution to adjust fluidly—and a source of ongoing political debate.

Nature, Recognition, and Limitations

The courts have repeatedly confirmed that conventions are important to the functioning of government, but do not have the character of law (see Attorney General v Jonathan Cape [1976]). Conventions may sometimes influence or shape judicial interpretation of law—especially where ethical expectations are so embedded as to shape expectations about government behaviour—but no enforcement or legal remedy is available for their breach.

Key Term: non-legal rules
Rules that, while not enforceable in law, are important for the operation of government and public institutions (for example, constitutional conventions).

The Royal Prerogative

The UK executive (the government) possesses a range of powers traditionally derived from the Crown, known as royal prerogative. These powers, now in practice exercised by government ministers, are the residue of the Crown’s historic authority not overridden or limited by statute. The royal prerogative includes powers such as appointing ministers, issuing passports, declaring war, making treaties, and granting honours.

Key Term: royal prerogative
The residual and discretionary powers historically possessed by the Crown, now largely exercised by modern government ministers, not derived from statute. Prerogative powers exist only so far as Parliament has not abolished or restricted them by legislation.

Parliament may abolish, override, or limit the prerogative by statute, as affirmed by the courts (see Attorney General v De Keyser’s Royal Hotel Ltd [1920]). The government cannot use the royal prerogative to override statutory provisions. In recent years, the scope and exercise of prerogative powers have increasingly come under judicial review, especially in areas relating to individual rights or significant rules of government (see R (Miller) v Secretary of State for Exiting the EU [2017]).

Some prerogative powers are closely regulated by constitutional convention (for example, that the monarch acts on the advice of the Prime Minister).

Key Term: residual liberty
The common law presumption that individuals are free to do anything not expressly prohibited by law (statute or common law).

Retained EU Law: Post-Brexit Continuity

Following Brexit, the status and application of EU-derived law in the UK shifted dramatically. To avoid legal gaps, the European Union (Withdrawal) Act 2018 “saved” the bulk of EU law in force immediately before exit day as "retained EU law." Retained EU law is a unique source: UK law of EU origin that continues to have effect unless and until amended or repealed by Parliament.

Key Term: retained EU law
UK law derived from the EU and preserved by the European Union (Withdrawal) Act 2018 after Brexit. It includes EU regulations, decisions, and directives as implemented in UK law, as well as associated case law and “general principles” of EU law in effect before exit day.

Retained EU law encompasses:

• Direct EU legislation (regulations and decisions) that applied before Brexit and now have effect as domestic law.
• UK Acts and regulations that were enacted to implement EU directives.
• Directly effective rights, obligations, and remedies that were recognised before Brexit.

Retained EU law is classified as either "retained direct principal EU legislation" (e.g., former EU Regulations) or "retained direct minor EU legislation" (e.g., tertiary EU act), with different amendment procedures and judicial status. Notably, while the general principle of supremacy of EU law does not apply to new UK laws made after Brexit, retained EU law may still prevail over conflicting domestic law passed before exit day. However, Parliament and devolved legislatures can amend or repeal retained EU law as they see fit.

Key Term: supremacy of EU law
The rule that, while the UK was an EU member, any provision of EU law took precedence over any conflicting provision of domestic law. As retained EU law, this supremacy continues only in relation to pre-Brexit UK laws unless or until changed by new legislation.

UK courts interpret retained EU law in light of pre-2021 decisions of the Court of Justice of the European Union, but are permitted to depart from those rulings in certain circumstances (the Supreme Court or Court of Appeal may depart “where it appears right to do so”).

Worked Example 1.4

A UK regulation implementing an EU directive is challenged after Brexit. Does it still have legal effect?

Answer:
Yes. If it was in force immediately before Brexit, it is retained EU law and remains effective unless changed by Parliament.

Retained EU law cannot be used to challenge the validity of Acts of Parliament, but it may be relied upon in judicial review of public bodies. Much of retained EU law affects important areas of law including employment, environmental law, and consumer rights.

Interaction and Hierarchy of Sources

When different sources of constitutional law conflict, the principle of parliamentary sovereignty determines that statute prevails over common law, prerogative, and retained EU law (to the extent assigned by Parliament). Common law, in turn, prevails over royal prerogative unless explicitly restricted or altered by Parliament. Conventions and non-legal rules may shape interpretation or political conduct but never override the law.

While the UK parliament remains legally supreme, modern developments—such as the Human Rights Act 1998 and the legacy of EU membership—have introduced new forms of legal scrutiny and have, on occasion, practically limited the scope of parliamentary sovereignty, especially due to political, not legal, factors.

Summary Table

Key Point Checklist

This article has covered the following key knowledge points:

• The UK constitution comprises both legal and non-legal sources: statutes, common law, judicial precedent, constitutional conventions, the royal prerogative, and retained EU law.
• Statutes (Acts of Parliament) are the most authoritative source, reflecting and enforcing parliamentary sovereignty, and override other sources in case of conflict.
• Parliamentary sovereignty means that the UK Parliament can legislate on any matter; only Parliament—or statute—can override an Act of Parliament.
• Constitutional statutes are key laws but may be amended or repealed by Parliament; they are protected from implied repeal but not from express repeal.
• The common law, shaped by judicial decisions and precedent, fills gaps and articulates significant constitutional principles, such as the rule of law, judicial review, and residual liberty.
• Judicial precedent ensures consistency and certainty in the interpretation and development of the law, with clear rules about which courts bind others.
• Constitutional conventions are important for the smooth working of government but are not legally enforceable by courts.
• The royal prerogative consists of non-statutory executive powers of government; these exist only insofar as Parliament has not expressly overridden them and are increasingly circumscribed.
• Retained EU law, created after Brexit, maintains continuity of EU-derived law within UK legal order unless and until Parliament amends or repeals it. Its supremacy is limited, applying only to conflicts with pre-Brexit statutes.
• In the hierarchy of sources, statute law is supreme. Common law ranks below statute; the royal prerogative below both unless statute or the common law provides otherwise. Conventions and non-legal rules operate at the political level.

Key Terms and Concepts

• constitution
• statute
• supremacy of statutes
• supremacy of eu law
• retained eu law
• common law
• judicial precedent
• rule of law
• residual liberty
• constitutional convention
• ministerial responsibility
• royal prerogative
• non-legal rules