The United Kingdom does not have one specific constitutional document named as such. Instead, the so called constitution of the United Kingdom, or British constitution, is a sum of laws and principles that make up the country's body politic. This is sometimes referred to as an "unwritten" or uncodified constitution. The British constitution primarily draws from four sources: statute law (laws passed by the legislature), common law (laws established through court judgments), parliamentary conventions, and works of authority. Similar to an entirely written constitution, this sum also concerns both the relationship between the individual and the state and the functioning of the legislature, the executive, and the judiciary.
Since the Glorious Revolution of 1688, the concept of parliamentary sovereignty has been the bedrock of the British legislative constitution, that is, the statutes passed by Parliament are the supreme and final source of law in the UK. It follows that Parliament can change the constitution simply by passing new statutes through Acts of Parliament. There has been some debate about whether parliamentary sovereignty remained intact in the light of the UK's membership in the European Union (EU), an argument that was used by proponents of leaving the EU in the 2016 referendum vote ("Brexit"). Another core constitutional principle, the rule of law, is a phrase that was popularized by legal scholar A. V. Dicey in his 1885 work, Introduction to the Study of the Law of the Constitution, which is recognized as a work of authority on the constitution by the British Parliament.
Acts of Parliament are bills which have received the approval of Parliament – that is, the Monarch, 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 Monarch to refuse to assent to a bill, though the possibility was contemplated by George V in relation to the fiercely controversial Government of Ireland Act 1914. Acts of Parliament are among the most important sources of the constitution. According to the traditional view, Parliament has the power to legislate however it wishes on any subject it wishes. For example, most of the iconic medieval statute known as Magna Carta has been repealed since 1828, despite previously being regarded as sacrosanct.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 medieval 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. One consequence of the principle of parliamentary sovereignty is that there is no hierarchy among Acts of Parliament: all parliamentary legislation is, in principle, of equal validity and effectiveness. However, the judgment of Lord Justice Laws in the Thoburn case in 2002 indicated that there may be a special class of "constitutional statutes" such as Magna Carta, the Human Rights Act 1998, the European Communities Act 1972, the Acts of Union and Bill of Rights which have a higher status than other legislation. This part of his judgment was "obiter" (i.e. not binding) – and, indeed, was controversial. It remains to be seen whether the doctrine will be accepted by other judges.