The UK has no single constitutional document comparable to the Constitution of the United States. It is therefore often said that the country has an "unwritten" or de facto constitution. However, the majority of the British constitution does exist in the written form of statutes, court judgments and European treaties. The constitution has other unwritten sources, including parliamentary constitutional conventions (more than most countries except New Zealand and Israel) and the royal prerogatives.
The bedrock of the British constitution has traditionally been the doctrine of Parliamentary sovereignty, according to which the statutes passed by Parliament are the UK's supreme and final source of law. It follows that Parliament can change the constitution simply by passing new Acts of Parliament. However, the UK's membership of the European Union has arguably complicated this principle. The European Communities Act 1972 means the UK applies all EU law (and disapplies any provisions of its own which conflict) that it passes in common with other member states.
Changing attitudes may also be seen among the judiciary: for example, the judgments of the Court of Appeal and the House of Lords in the Jackson litigation arising out of the Hunting Act 2004 indicate that senior judges may no longer necessarily be prepared to view Acts of Parliament as sacrosanct. The former Lord Chief Justice, Lord Woolf, has made comments to the same effect outside the courtroom.
Acts of Parliament are laws (statutes) that have received the approval of Parliament - that is, the Sovereign, the House of Lords and the House of Commons. On rare occasions, the House of Commons uses the "Parliament Acts" (the Parliament Act 1911 and the Parliament Act 1949) to pass legislation without the approval of the House of Lords. It is unheard of in modern times for the Sovereign to refuse to assent to a bill, though the possibility was reportedly contemplated in relation to the fiercely controversial Irish Home Rule Act 1914.
Acts of Parliament are among the most important sources of the constitution. According to the traditional view, Parliament has the ability to legislate however it wishes on any subject it wishes. For example, most of the iconic mediaeval statute known as Magna Carta has been repealed since 1828, despite previously being regarded as sacrosanct. It has traditionally been the case that the courts are barred from questioning any Act of Parliament, a principle that can be traced back to the mediaeval period. On the other hand, this principle has not been without its dissidents and critics over the centuries, and attitudes among the judiciary in this area may be changing.
Treaties do not, on ratification, automatically become incorporated into UK law, though they are still binding on the United Kingdom in international law. Important treaties have been incorporated into domestic law by means of Acts of Parliament. The European Convention on Human Rights has, for example, to a considerable extent been incorporated into domestic law through the Human Rights Act 1998.
On one analysis, EU law is simply a subcategory of international law that depends for its effect on a series of international treaties (notably the Treaty of Rome and the Maastricht Treaty). It therefore has effect in the UK only to the extent that Parliament permits it to have effect, by means of statutes such as the European Communities Act 1972, and Parliament could, as a matter of British law, unilaterally bar the application of EU law in the UK simply by legislating to that effect.
On another analysis, which was first authoritatively articulated by the European Court of Justice in the 1963 case of Van Gend en Loos, EU law represents a new legal regime which is qualitatively different from other forms of international law and which takes precedence over the internal legal and constitutional arrangements of member states. On this view, the notion that Parliament could unilaterally legislate "as a matter of British law" to withdraw the UK from the ambit of EU law is anachronistic and unreal.
In any event, British membership of the EU has had a very considerable impact on the constitution and governance of the country. In the Factortame litigation, for example, the House of Lords took the unprecedented step of granting an injunction to "disapply" an Act of Parliament (the Merchant Shipping Act 1988). While this step can in principle be argued to be consistent with traditional ideas of Parliamentary supremacy, it does illustrate the profound impact that EU membership has had. The merits and demerits of continued British involvement in the EU continue to be hotly debated within the UK.
As the United Kingdom uses the common law legal system, court judgments also form a source of the constitution: generally speaking, judgments of the higher courts form precedents or case law that binds lower courts and judges.
A constitutional precedent applicable to British colonies is Campbell v. Hall, which effectively extended those same constitutional limitations to any territory which has been granted a representative assembly.
Many British constitutional conventions are ancient in origin, though others (like the Salisbury Convention) date from within living memory. Such conventions, which include the duty of the Sovereign to act on the advice of his or her ministers, are not formally enforceable in a court of law; rather, they are primarily observed "because of the political difficulties which arise if they are not.
The royal prerogative is the collective name for a collection of powers belonging to the Sovereign which have no statutory basis. In practice, by convention, most of the prerogatives are now directly exercised by ministers, or at any rate on the advice of ministers.
The precise extent of the royal prerogative has never formally been delineated, but it includes the following powers:
The most important prerogative still personally exercised by the Sovereign is considered to be the appointment and dismissal of Prime Ministers. The last time this reserve prerogative was exercised by the monarch without reference to the Cabinet was with the appointment of Harold Wilson as Prime Minister in February 1974, despite his party not having a majority in the House of Commons. Queen Elizabeth II exercised her prerogative after extensive consultation with the Privy Council.
The Royal Prerogative is not unlimited; this was established in the Case of Proclamations (1611), which confirmed that no new prerogative can be created and that Parliament can abolish individual prerogatives.
Works of authority is the formal name for works that are sometimes cited as interpretations of aspects of the UK constitution. Most are works written by nineteenth- or early-twentieth-century constitutionalists, in particular A.V. Dicey, Walter Bagehot and Erskine May.
The fact that the modern British constitution has emerged from an "organic" process of evolution dating back to the Middle Ages, rather than through revolution and by design, has given it (according to one's perspective) either a valuable flexibility or a dangerous looseness. On the one hand, its loose texture arguably makes it responsive to political and social change, especially since many of its principles are simply conventions. On the other hand, the absence of mechanisms for entrenchment means that far-reaching changes could in theory be made without popular support.
Until recently, there was no modern statute or document that attempted to codify the rights of citizens (e.g. freedom of speech), in part because of the doctrine of negative rights, under which Britons were simply deemed to enjoy the right to do anything that was not specifically prohibited. The introduction of the European Convention on Human Rights in 1950 was held to have limited consequences for British law, since the rights protected by the Convention were said already to be protected by British common law -- a stance which can be seen either as reflecting the high status of civil rights in the UK or as evidencing an unjustified degree of complacency. The Convention became directly enforceable in the British courts under the Human Rights Act 1998, though the courts are still not permitted directly to invalidate statutes that conflict with its provisions.
The limits of the doctrine of Parliamentary sovereignty have been debated for a number of years. One purported example of its limits which is often given is provided by the category of statutes (such as the 1931 Statute of Westminster) that were passed to grant independence to former British colonies. It is said that it would clearly be beyond the power of Parliament to repeal legislation of this sort and to return the former colonies to British rule. The counter-argument is that Parliament could take such a step as a matter of British law even though it would have no physical means of enforcing it (just as, for example, Taiwan continues in principle to claim sovereignty over mainland China). One reply to this counter-argument is that a doctrine that allows such apparent absurdities must in itself be defective.
Following the accession of the UK to European Economic Community (now the European Union) in 1973, the UK became bound by European law and more importantly, the principle of the supremacy of European Union law. According to this principle, which was outlined by the European Court of Justice in 1964 in the case of Costa v. ENEL, laws of member states that conflict with EU laws must be disapplied by member states' courts. The conflict between the principles of the primacy of EU law and of parliamentary supremacy was illustrated in the judgment in Thoburn v Sunderland City Council, which held that the European Communities Act 1972, the Act that initiated British involvement in the EU, could not be impliedly repealed simply by the passing of subsequent legislation inconsistent with European law. The court went further and suggested that the 1972 Act formed part of a category of special "constitutional statutes" that were not subject to implied repeal. This exception to the doctrine of implied repeal was something of a novelty, though the court stated that it remained open for Parliament to expressly repeal the Act. It is politically inconceivable at the present time that Parliament would do so, and constitutional lawyers have also questioned whether such a step would be as straightforward in its legal effects as it might seem. It should also be noted that the Thoburn judgment was handed down only by the Divisional Court (part of the High Court), which occupies a relatively low level in the legal system.
The British constitution is parliamentary in character, and the executive ("Her Majesty's Government") is drawn from the legislature, Parliament. The doctrine of separation of powers is not as prominent in the British constitution as it is elsewhere.
Since the Government is "fused" with Parliament, and virtually every government has a majority, there is no formal restraint on the legislative power of the executive. This is broken only if Members of Parliament vote against a government bill, which, due to a strong whip system, happens extremely rarely -- the two most recent such votes occurred in 1986 and 2005. The phrase elective dictatorship was coined by former Lord Chancellor Quintin Hogg in 1976 to highlight the enormous potential power of government afforded by the constitution. This problem (if it is regarded as such) is relatively recent in its historical origin, since Parliament previously functioned (for example, after the "Glorious Revolution" of 1688-89) as a brake on the power of the monarch, who at that time was an independent political actor in his or her own right.
In practice, some principles and elements of the constitution, such as the rule of law, are so ancient and ingrained in the UK's political culture that they would be extremely difficult to abolish. Parliamentary sovereignty and the rule of law have been widely considered the most important principles of the constitution since the nineteenth century, and attempts to substantially circumvent them would likely be met with backlash by the electorate, or even the monarch (who appears to retain certain reserve powers).
In one article, Lord Scarman presents a spirited argument for a written constitution for the UK, but still refers to the 1688 compromise and resulting acts of parliament as a constitution.
The UK Constitution has no fundamental written source, and is ever changing. It relies much on unwritten convention. Dicey himself identified that ultimately "the electorate are politically sovereign," and Parliament is legally sovereign. Barendt argues that the greater political party discipline in the House of Commons that has evolved since Dicey's era, and the reduction in checks on governmental power, has led to an excessively powerful government that is not legally constrained by the observance of fundamental rights. A Constitution would impose limits on what Parliament could do without a legal majority. To date, the Parliament of the UK has no limit on its power other than the possibility of extra-parliamentary action (by the people) and of other sovereign states (pursuant to treaties made by Parliament and otherwise).
It has been claimed that the unwritten British Constitution is a refusal by people in power to communicate to those subject to that power the extent of that power and the rights available to prevent and/or effectively remedy the abuse of that power. The pressure group Revived Cornish Stannary Parliament believes that the unwritten British constitution constitutes a conspiracy against the British public. This is not a widely-held view. Support for a written constitution has been associated in particular with the Liberal Democrats and the pressure group Charter 88, though recently senior Labour government figures, including Gordon Brown and Jack Straw, have indicated that they are receptive to the idea. Proponents of a codified constitution and Bill of Rights argue it would strengthen the legal protection of democracy and freedom.
Recent reforms have also decentralised the UK by setting up a devolved parliament in Scotland and assemblies in Wales and Northern Ireland. The UK had previously been an essentially unitary state since its foundation in 1801, though Scotland had always had a separate legal system and Ireland had repeatedly been subject to attempts to devolve power from London. Some commentators have stated the UK is now a "quasi-federal" state: it is only "quasi" federal, because (unlike the other components of the UK) England has no legislature of its own, and is directly ruled from Westminster (it should be noted however that the devolved bodies are not sovereign and could, in theory at least, be repealed by Parliament - unlike "true" federations such as the United States where the constituent states share sovereignty with the federal government). Attempts to extend devolution to the various regions of England have stalled, and the fact that Parliament functions both as a British and as an English legislature has created some dissatisfaction (see, for example, the article on the "West Lothian question").
These reforms have undermined the concept of Parliamentary sovereignty somewhat, even though Parliament could still abolish the devolved assemblies and repeal the Human Rights Act. In reality such action is unlikely so these restrictions on the legislative power of Parliament are likely to remain on the statute book for the time being.
The passage of the Freedom of Information Act has challenged the traditional British notion that governments should not disclose too many details of their operations.
Recent changes also include the Constitutional Reform Act 2005 which alters the structure of the House of Lords to separate its judicial and legislative functions. For example the legislative, judicial and executive functions of the Lord Chancellor are now shared between the Lord Chancellor (executive), Lord Chief Justice (judicial) and the newly created post of Lord Speaker (legislative). The presence of Law Lords (members of the judiciary) in the House of Lords, will be removed by moving the Lords to the new Supreme Court of the United Kingdom by 2009.