Sources of the Constitution Lecture

The United Kingdom does not have a single document known as the 'Constitution' and as such, its constitution is not codified. In fact, even 'written constitutions' are merely a starting point for the full body of constitutional law, which elaborates upon the countries governance structure. Written documents might offer fundamental constitutional principles, but there are further texts which supplement and elaborate upon the basic principles. Ordinary legislation is drafted in order to provide fuller information about those basic principles which are stated in the constitution.

In a common law system, the courts also interpret the statutory legislation by clarifying points of law which require interpretation. Judicial precedent in England and Wales binds lower courts and creates a series of judicial decisions which itself can be considered a source of constitutional law. Finally, informal resolutions between parties in constitutional matters can be made where there is no legislative solution to an issue. Constitutional conventions or political precedents can be created in this way when relevant parties show evidence of being willing to adhere to the resolution to the issue.

The UK's absence of a codified constitution makes the scope of the sources, which would be correctly labelled as 'constitutional' less clear-cut than a situation where there is a codified constitution. Geoffrey Marshall explains:

'[N]o easy logical limit can be set to the labour of the constitutional lawyer ... any branch of the law, whether it deals prima facie with finance or crime or local government, may throw up constitutional questions' (Constitutional Theory, Clarendon Press, 1971: 6).

The disadvantage of this lack of clarity can be highlighted by the legal protection of civil liberties and human rights prior to the Human Rights Act 1998 where no comprehensive enforceable Code or Bill of Rights. At that time all that existed was the text of the European Convention on Human Rights 1950, which was not enforceable directly in the UK courts and common law. It was not clear to the individual citizen what their rights were and to seek a remedy against a breach of a Convention right, they had to apply to the European Court of Human Rights in Strasbourg.  when there was no comprehensive, enforceable modern bill of rights. Rights were protected by statute and common law, but the European Convention on Human Rights 1950 was not directly enforceable in the domestic courts. Once the UK accepted individual petitions in 1966, individuals could seek a Convention remedy in Strasbourg after exhausting effective domestic remedies, initially through the European Commission of Human Rights.

The Human Rights Act 1998 enabled individuals to rely on the Convention rights defined in section 1 in the UK courts. Most of its provisions came into force on 2 October 2000. In order to understand the United Kingdom's constitution, which is uncodified, it is necessary to consider a number of legal and non-legal sources. The legal sources include Acts of Parliament and judicial decisions which regulate the relationship between the state and its citizens. Legal sources also include the Royal Prerogative, EU-derived law given effect by statute, and relevant decisions of the European Court of Human Rights. The principle non-legal source of the constitution are constitutional conventions which are politically binding on government Ministers and those in public office.

(a) Acts of Parliament

Members of the House of Commons (elected) and of the House of Lords (unelected) normally approve bills before they receive royal assent. Government bills are drafted by parliamentary counsel and scrutinised during the legislative process. A large proportion of the UK's constitutional arrangements are now laid down in statutes. Under the Parliament Acts 1911 and 1949 certain bills can receive royal assent without the agreement of the Lords. A great deal of legislation is concerned with the allocation and organisation of power to, the institutions of government. In 2003, the Joint Committee on the Draft Civil Contingencies Bill drew up a list of statutes, which were considered to be fundamental elements of constitutional law. The first of these statutes was the Magna Carta 1297, which proclaims that a free man may be imprisoned only by lawful judgment of his peers or by the law of the land, and that justice should not be sold, denied or delayed. 

The Joint Committee on the Draft Civil Contingencies Bill included the following in its list: Crown and Parliament Recognition Act 1689, Act of Settlement 1700, Union with Scotland Act 1706 (described in the report as the Act of 1707), Union with Ireland Act 1800, Parliament Acts 1911 and 1949, Life Peerages Act 1958, Emergency Powers Act 1964, European Communities Act 1972, House of Commons Disqualification Act 1975, Ministerial and Other Salaries Act 1975, British Nationality Act 1981, Supreme Court Act 1981 (now the Senior Courts Act 1981) and the Representation of the People Act 1983. The list also included the Northern Ireland Act 1998, the House of Lords Act 1999 and the proposed Civil Contingencies Act. As enacted, section 23(5) of the Civil Contingencies Act 2004 prevents emergency regulations from amending Part 2 of that Act or the Human Rights Act 1998.

Several of these Acts have now been amended or repealed. There are also a number of Acts which have been passed through Parliament since 2003 that address constitutional matters, these include the Constitutional Reform Act 2005, the Tribunals, Courts and Enforcement Act 2007, the Parliamentary Standards Act 2009, the Constitutional Reform and Governance Act 2010, the Localism Act 2011, the European Union Act 2011 (since repealed), the Recall of MPs Act 2015, the House of Lords (Expulsion and Suspension) Act 2015, the Wales Act 2014 and the Scotland Act 2016. More recent examples include the European Union (Withdrawal) Act 2018, the Dissolution and Calling of Parliament Act 2022 and the House of Lords (Hereditary Peers) Act 2026.

(b) The Common Law

Another important source of the United Kingdom's constitutional rules can be found within the law reports, which report on the important judicial decisions made within the court system. Judges in England and Wales, Scotland and Northern Ireland have all contributed to the development of constitutional principles within the UK. The Constitutional Reform Act 2005 established the UK Supreme Court, which began work in 2009. It is the final court of appeal in civil cases throughout the UK and in criminal cases in England, Wales and Northern Ireland. In Scottish criminal proceedings its jurisdiction is confined to particular constitutional questions. The courts of appeal in England and Wales and in Northern Ireland, and the senior Scottish courts, also develop constitutional principles. Views differ as to the amount of influence that UK judges and judges sitting in the Strasbourg court (the European Court of Human Rights) and the Luxembourg court (the Court of Justice of the European Union) should have in deciding upon the appropriateness of acts of the UK Parliament and UK government.

The principle role of courts is in the application of the law to the facts of a case and resolving disputes between litigants. However, judicial precedent is more complicated than this; cases with a constitutional dimension to them are capable of making public law. Judicial precedent is a source of constitutional law in three senses. Firstly, in the interpretation of constitutional legislation; legislation may be clear or unspecific or not cover a specific set of facts. Courts determine the meaning of the statutory language in its context and whether it extends to a specific set of facts.

The second role of the courts in a common law system in relation to the constitution is the creation of a body of judge-made law. Much of the civil law is based upon the common law, which are legal principles, which are expressed by the judges on a case-by-case basis. In situations where government Ministers exercise discretionary powers, for example on British citizenship, the Minister is required to act in accordance with certain principles of good administration. There are general principles, which have been developed via the common law that apply generally to the decisions of public bodies. Such principles are enforced through the process of Judicial Review, which is the means through which the decisions of public bodies can be challenged within the courts.

Common law constitutional principles are also a judge-made source of public law. The principle of legal certainty is an example of such a principle. It means that people should know what the law is in order to choose to regulate their conduct as to act in accordance with it. This principle has a relevance of a political nature; governments are expected to act within this principle. Courts presume that legislation does not impose criminal liability retrospectively. Article 7 of the European Convention on Human Rights prohibits conviction for conduct which was not criminal under national or international law when it occurred. Under the common law principle of legality, general or ambiguous statutory wording does not override fundamental rights (R v Secretary of State for the Home Department, ex parte Simms [2000] 2 AC 115).

Finally, the royal prerogative is considered to be part of the common law, in that it authorises the executive branch of government to carry out certain acts such declaring war, or granting honours. It is a historical legacy of powers once exercised personally by the monarch. Statute has displaced many prerogative powers. Ministers exercise some of the remaining powers directly and advise the monarch on the exercise of others.

(c) European Law

The United Kingdom joined the European Communities in 1973. In the referendum of 23 June 2016, 52% of those who voted elected to leave the European Union. The UK left on 31 January 2020. The European Union (Withdrawal) Act 2018 repealed the European Communities Act 1972, whose effect was saved with modifications until the transition period ended on 31 December 2020. Much EU-derived law continued as domestic law. Under the Retained EU Law (Revocation and Reform) Act 2023, the retained EU law remaining at the end of 2023 became known as assimilated law, and the general principle of EU supremacy was abolished in domestic law for matters occurring after the end of 2023. Section 7A of the 2018 Act continues to give effect and priority to applicable Withdrawal Agreement rights and obligations, including those under the Windsor Framework.

EU membership changed what was possibly the most basic rule of the UK constitution. In Case 6/64 Flaminio Costa v ENEL [1964] ECR 585 the court of the European Economic Community (the forerunner to the European Union) held in a landmark decision that European Community law has supremacy over national law. In the UK, the priority given to applicable Community law by the 1972 Act raised the question of Parliamentary sovereignty. The impact of this ruling was illustrated in R v Secretary of State for Transport, ex parte Factortame Ltd. and ors (No.1) [1990] 2 AC 85, when Spanish owners of fishing vessels argued that they had been discriminated against on the ground of nationality and the courts were asked to suspend application of the disputed provisions of the Merchant Shipping Act 1988. The House of Lords referred the question of interim relief to the European Court of Justice (Case C-213/89). Following its ruling, the House granted interim relief in Factortame (No. 2) [1991] 1 AC 603.

In Thoburn v Sunderland City Council [2003] QB 151, Laws LJ held that ordinary implied repeal did not apply to constitutional statutes. While the European Communities Act 1972 remained in force, an inconsistent later provision did not by itself displace the rights given effect by that Act. Section 18 of the European Union Act 2011, since repealed, confirmed that directly applicable or directly effective EU law was recognised in the UK by virtue of an Act of Parliament. In Allister [2023] UKSC 5, the Supreme Court gave effect to the clear terms of section 7A of the 2018 Act even where they modified the effect of the Acts of Union.

The European Convention on Human Rights 1950 is an agreement of the Council of Europe and not of the European Union. The UK remains a party to the Convention. Under section 2 of the Human Rights Act 1998, UK courts and tribunals must take account of relevant Strasbourg decisions when considering a question concerning a Convention right. That duty applies to decisions predating the Act as well as later decisions, including those on proportionality.

(d) International Law

International Treaty law can have an influence on and is sometimes a source of constitutional law.  International and bi-lateral treaties are often given effect within UK domestic law, for example, rights from the European Convention on Human Rights and Fundamental Freedoms 1950 have been given effect in UK law by means of the Human Rights Act 1998. The ECHR and the UK-EU Withdrawal Agreement, through the effect of national legislation, have significant impact upon the UK's constitutional arrangements.

International law has long included both treaties and custom. Agreements such as the Slavery Convention 1926 affected the treatment of individuals well before the 1950s. In more recent years, transnational institutions, such as the United Nations, and treaty law, are increasingly influencing what happens within national constitutional systems. International organisations such as the World Trade Organisation (WTO) provide rules for trade between members and a mechanism for settling disputes under the covered agreements.

Since the end of the Second World War, a wide body of international human rights agreements have also been established, with treaty bodies that monitor how states implement the major UN human rights treaties. Human rights and fundamental freedoms of individuals are no longer merely an issue between governments and their people; instead governments have signed up to agreements requiring them to protect the people within the scope of each treaty. A state generally cannot invoke its domestic law as a justification for breaching a treaty. Whether a treaty right is enforceable in a domestic court is a separate question.

Two main sources of international law are treaties and customary international law. Article 38 of the Statute of the International Court of Justice also identifies general principles of law, and judicial decisions and scholarly writings as subsidiary means of determining rules of law. Treaty law is an agreement under international law, usually between states, but international organisations can also be subjects of international law. The Vienna Convention on the Law of Treaties 1969 provides the internationally accepted rules on treaty interpretation and applies to written treaties between states. Article 3 preserves the legal force of other international agreements, including oral agreements.

Customary International Law

Customary international law is unwritten law, and is formed by two constituent elements: state practice and opinio juris.  State practice must be sufficiently widespread, representative and consistent, and accepted as law. No particular duration is required. The UK regards self-defence against an imminent armed attack as permitted by customary international law, relying on the diplomatic correspondence following the Caroline incident of 1837. The scope of anticipatory self-defence is disputed. Certain rules of customary international law take on the status of jus cogens. Jus cogens norms are accepted and recognised by the international community of states as a whole as permitting no derogation. A treaty conflicting with an existing peremptory norm is void, and only a subsequent peremptory norm can modify such a norm. The prohibition of torture and the prohibition of genocide are considered rules of jus cogens.

The relationship between customary international law and English law has long been debated. In Chung Chi Cheung v R [1939] AC 160, at 167-168, Lord Atkin explained that the courts ascertain the rule which nations accept amongst themselves and treat it as incorporated into domestic law so far as it is consistent with statute and rules finally declared by the courts.

The difficulty with this approach is that through the doctrine of judicial precedent it risks incorporating outdate versions of international rules into national law. The Court of Appeal in Trendtex Trading Corporation v Central Bank of Nigeria [1977] 1 QB 529 acknowledged that the rules of customary international law change over time . Lord Denning MR held that the courts could recognise such a change despite an earlier decision on the former rule. Customary international law can inform the development of the common law, subject to statute and domestic constitutional principles (R (Keyu) v Secretary of State for Foreign and Commonwealth Affairs [2015] UKSC 69). An Act of Parliament prevails in domestic law where it conflicts with a customary or treaty rule.

Treaty Law

The other main source of international law is treaty law. Treaties are international agreements governed by international law, usually between states. International treaties cover a significant area of public international law, including the law of the sea, humanitarian law, human rights laws, the law on the use of force, environmental law and international commercial and trade law. Many of these international agreements have been negotiated through the auspices of the United Nations.

Treaties can be bi-lateral agreements between two states, or multilateral treaties, between a number of states. International agreements such as the United Nations Convention on the Rights of the Child 1989 and the United Nations Framework Convention on Climate Change 1992 are almost universally ratified. Major instruments can also be regional, such as the African Charter on Human and Peoples' Rights 1981 (the Banjul Charter) or the Charter of the Arab League 1945.

Constitutional systems vary in the terms of how they recognise treaties. Generally, there are two different approaches in this regard. A 'monist' system gives treaties that it enters into domestic effect; the treaty becomes a source of law that can be applied within national courts. The UK takes a 'dualist' approach to its international treaty obligations. Treaty-making is generally an executive power. Under Part 2 of the Constitutional Reform and Governance Act 2010, treaties subject to its ratification procedure must normally be laid before Parliament for 21 sitting days. Ratification alone does not change domestic law. Treaties can inform the development of the common law and the interpretation of legislation, but enforceable domestic rights require a basis in domestic law. Parliament can legislate contrary to a treaty, even though the UK may thereby breach its international obligations. The Children Act 1989 preceded adoption of the UN Convention on the Rights of the Child 1989. The United Nations Convention on the Rights of the Child (Incorporation) (Scotland) Act 2024 makes it unlawful for public authorities to act incompatibly with the incorporated requirements in exercising functions covered by the Act. In Wales, the Rights of Children and Young Persons (Wales) Measure 2011 requires Welsh Ministers to have due regard to the Convention requirements when exercising their functions.

(e) Constitutional Conventions

There are many important constitutional matters in the UK for which no law exists. In such instances, it is necessary to resort to non-legal constitutional sources, also known as constitutional conventions. One of the most important conventions in the UK constitution is that a government or Prime Minister who cannot command the confidence of the House of Commons is expected to resign or, where appropriate, request a dissolution. If a general election gives an opposition party a clear majority, the outgoing Prime Minister resigns and the monarch invites the leader of the majority party to form a new government. AV Dicey in Introduction to the Study of the Law of the Constitution (1885) distinguishes between law and conventions. Laws are enforceable in the courts. There are no judicial remedies or penalties if conventions are violated.

If Labour won a clear majority against a Conservative government, the Conservative Prime Minister would be expected to resign, and the monarch would then request the leader of the Labour Party to form a new government. Although it would be unthinkable if upon losing a general election, the previous government did not resign, there is no law that requires this to take place. The Prime Minister could fail to resign in the face of a clear opposition majority, or the monarch could request the Green Party to form a government, even though the Labour Party won the election. In such circumstances, neither the monarch nor the Prime Minister would be subject to legal sanction.

In such circumstances, legal freedom is constrained by political precedent. Although there is no law to give it effect, there is a clear and long standing political precedent or constitutional convention that on a change of government the monarch will ask the leader of the majority party to form a government. Such rules are not found uniquely in systems like the UK that are without a codified constitution; they can also play a similar role in elaborating upon the rules within a codified constitution.

In the United States, prior to 1951, there was no legal rule which established a limit upon how many terms of office a President could serve. It was widely accepted that two terms was the maximum number that any President could serve; this convention was broken by Franklin D. Roosevelt, who was elected four times. This political rule was then incorporated into law by an amendment to the US Constitution in 1951 to limit a person to being elected President twice, or once if they served more than two years of a term to which another person was elected (22nd Amendment to the US Constitution).

Such rules are established through habitual and customary practices within government although in recent years these conventions have been codified and formalised in a gradual manner. One important example in the UK is the Ministerial Code. Written instructions to government Ministers were for many years confidential. By convention, government Ministers are obliged to account to Parliament for the policies, decisions, and actions of the institutions of government. The instructions were first published as Questions of Procedure for Ministers in 1992 and appeared under the title Ministerial Code in 1997. This document sets out the standards to be adopted by government ministers.

David Cameron issued a version of the Ministerial Code in October 2015. The current edition dates from October 2025. The Ministerial Code sets out standards regarding ministerial conduct in areas such as matters of the crown, the government, in appointments, private interests and travel. Despite the existence of the Code, it is not clear whether government Ministers are adequately held to account by Parliament.

Constitutional conventions also exist in a situation of a 'hung' Parliament (i.e. when no political party wins an overall majority in a general election, such as occurred in 2010). Prior to the 2010 election, the Cabinet Secretary provided draft guidance to the House of Commons Justice Committee, Constitutional Processes Following a General Election (HC 396 2009-10).  When a hung Parliament resulted from the 2010 election, the draft guidance was used in clarifying the constitutional position, which enabled the coalition government to be formed, by the Conservative Party and Liberal Democrats.

How are conventions created?

Since conventions are not laws, they are not passed through Parliament in the form of legislation nor are they decisions made by judges in court, how then are they created?  Dicey stated that constitutional conventions are constitutional morality and defined them as 'understandings, habits or practices' that 'regulate the conduct of the several members of the sovereign power, of the Ministry, or of other officials' (Dicey, Introduction to the Study of the Law of the Constitution, London, 1959:p.24).

Constitutional conventions deal with constitutional matters; they operated in a manner that is supplementary to the law. Those to whom the convention is aimed consider themselves to be bound by it, even though they are not binding in a legal sense. Conventions can be established through precedent or agreement. A single precedent may suffice if there is good reason for the rule. Conventions give effect to underlying constitutional principles. Democracy is the constitutional principle, which underlies the constitutional convention that when a new government is needed the monarch should invite the person best placed to command the confidence of the House of Commons to form it.

The Jennings Test can be found in: Ivor Jennings, The Law and the Constitution University of London Press, 1963, p.163. The test purports to determine whether a political practice or rule can be correctly regarded as a constitutional convention, it states

1. What are the precedents?
2. Did the relevant actors believe themselves to be bound by the rule?
3. Is there a rationale for the rule?

In general, constitutional conventions are binding political rules. Some authors have distinguished between binding and non-binding conventions. KC Wheare, in The Statute of Westminster and Dominion Status, 5th edn, 1953 distinguishes between usages and conventions. The former is non-binding where the later is. G Marshall and GC Moodie in Some Problems of the Constitution (1971) draw a distinction between obligatory and non-obligatory rules. To be an obligation a rule must prescribe something if it is to confer an obligation of state. Description thus does not confer a rule and is non-binding.

Why are Constitutional Conventions Observed?

Constitutional conventions are unenforceable by courts but yet are observed and respected. However, laws also reflect a personal sense of morality, so an individual might desist from murder due to personal morality, rather than merely because it is subject to criminal sanction. Furthermore, people might abide by rules not based on their own sense of morality but because the majority of people respect a certain system of rules. People also chose to abide by rules because of the stigmatising effect of breaching societies norms.

The reasons why people obey rules helps us to understand why people obey constitutional conventions. Since all important constitutional conventions are simply a practical application of fundamental constitutional principles, which are by definition widely accepted and deeply rooted. Further, constitutional actors may not personally agree with a particular principle underlying a convention, but since a majority of people seem to agree with it, they are inclined to accept the majority view. Actors may also respect constitutional rules for self-serving reasons. Politicians in government may choose to abide by conventional rules for fear that the failure to do so would incline opposition politicians when in power to do likewise. The prescriptive nature of constitutional conventions does not derive from legal rules, but from morality, a wish to adhere to a majority view and through self-interest.

Conventions are not always respected, like legal rules, they may be breached, however this breach may not lead to any significant consequences. An example of this is the convention regarding the former twice-weekly attendance of the Prime Minister at the House of Commons to answer MP's questions. Tony Blair dispensed with this convention in 1997 by replacing two fifteen-minute sessions with one half-hour session each sitting week. While the underlying principle was maintained the specific details of how that should be achieved was able to be disregarded.

The breach of some conventions might have quite significant consequences. The refusal of the monarch to give their assent to a Bill approved by Parliament, might call the whole question of the monarchy into question. If a Cabinet were found to be in breach of important constitutional conventions, the whole government might be required to resign and a general election called.

Although conventions themselves are not legally enforceable, they are on occasion turned into law through the enactment of legislation. During the constitutional crisis of 1909-11, the House of Lords (then dominated by Conservative peers) refused to pass a finance bill that had been endorsed by the House of Commons. The Liberal government took steps to enforce the constitutional convention through the Parliament Act 1911, which allows a Money Bill certified by the Speaker and passed by the Commons to receive royal assent without the Lords' agreement. It must be sent to the Lords at least a month before the end of the session and remain unpassed by them without amendment for a month.

Although constitutional conventions are not legally enforceable, certain case law suggests that conventions are not wholly legally irrelevant.  A convention can influence the application of the law to the facts of a case. Collective responsibility requires Cabinet Ministers to treat Cabinet discussions with confidentiality. In Attorney General v Jonathan Cape Ltd [1976] QB 752, the government sought an injunction against the publication of a former Cabinet Ministers memoirs in that they contained details of Cabinet meetings; the publication of which would breach the convention of confidentiality. The court recognised that the public interest in collective responsibility could support an injunction for breach of confidence. It refused relief because disclosure after the time that had elapsed would no longer inhibit free Cabinet discussion. In R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5, statutory recognition of the Sewel convention did not make the devolved legislatures' consent a legal condition of Westminster legislation.

f) Hierarchy of Constitutional Sources

Constitutions are usually regarded as the highest form of law in a country; written constitutions are nearly always hierarchically superior to other forms of legislation.  The form of constitutional review varies. In France, under articles 61, 61-1 and 62 of the Constitution, the Constitutional Council can prevent promulgation of an unconstitutional provision or, on a reference arising from litigation, repeal a provision infringing constitutionally guaranteed rights or freedoms with effect from publication of its decision or a later date it sets. In the UK, courts do not generally have power to strike down an Act of the UK Parliament. They can declare legislation of a devolved legislature outside its statutory competence, and specified courts can declare Westminster legislation incompatible with a Convention right under section 4 of the Human Rights Act 1998 without invalidating it.

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