United Kingdom has an uncodified constitution, which means it is not all contained in a single document. There are several sources of the constitution, some being written down and some not. The notion that the Constitution of the United Kingdom is unwritten is not strictly correct.
Key principles
The key principles of the constitution are its underlying features. The two most important principles have existed for a very long time, since the creation of Parliament. They were identified by the constitutional lawyer, A.V. Dicey as the twin pillars of the constitution:
European Union membership, the principle that EU law takes precedence over UK law. This principle was famously identified in the Factortame case in which the Merchant Shipping Act 1988 was overturned. This appears to undermine the principle of Parliamentary sovereignty, but Parliament could still withdraw from the EU by repealing the European Communities Act 1972, so in a way Parliamentary sovereignty is preserved.
Sources
There are several sources of the constitution. Not all of the sources are written down (for example, some are contained in conventions), but it is incorrect to say the UK has an "unwritten constitution" because much of it is written down.
Since entrenched "constitutional law" does not exist, the UK constitution is flexible, as opposed to rigid constitutions such as the Constitution of the United States.
The two most important principles of the Britishconstitution were first established to exist as the "twin pillars" of the constitution by A.V. Dicey, in his work An Introduction to the Study of the Law of the Constitution (1885).
Constitutional monarchy is a key principle, meaning that the monarch does not actually rule, they have a ceremonial role only.
The British North America Acts 1867–1975 are a series of Acts of the BritishParliament dealing with the government of Canada.
Canada and the other British dominions achieved full legislative sovereignty with the passage of the Statute of Westminster 1931, but prior to the Canada Act 1982 the British North America Acts were excluded from the operation of the Statute of Westminster and could only be amended by the BritishParliament.
By the Canada Act 1982, the BritishParliament, acting at the request and with the consent of Canada, enacted the Constitution Act 1982, which established a procedure for the amendment of the Canadian constitution by the Canadian Parliament.