The constitution is a set of rules and values defining and limiting the use of power by which to guarantee the rights and freedom of people. The UK constitution, in nature, is uncodified due to the doctrine of Parliamentary Sovereignty, which reflects the fact that Parliament can legislate in any area it chooses, potentially rendering a written constitution amendable by future Parliaments.
There are several positives in having an uncodified (unwritten) constitution in the UK:
The uncodified constitution
Sir Ivor Jennings “clearly the UK has such constitution and rules as the document would set out.”
The flexibility of the uncodified constitution has allowed the UK to adapt to changing circumstances. For example, the debate in the United States over the second amendment on the right to bear arms. It was passed at the time of rebellion. It is probably now too continuous to have the high consensus necessary to change it. Constitutional amendments in the United States require a two-thirds majority in the House of Representatives and the Senate. As a result, although the United States has a written constitution, it was only amended once in the last 40 years.
By contrast, the UK constitution has changed substantially over the years. For example, the UK has entered the EU and left, all with a simple majority required in Parliament. It could be said that the unitary nature of the UK contributed towards having a flexible constitution, unlike the United States, whose federal nature has made a rigid constitution a form of necessity.
The sources of the UK constitution
The UK constitution is derived from:
Statute;
Case law,
Prerogative powers;
Conventions; and
EU law at the time in which the UK was a EU member.
Statute
The Parliament Act 1911 and 1949 were both with significant constitutional impacts. Both altered the structure of power by limiting the power of the Lords giving the common more dominance.
The European Communities Act 1972 incorporated EU law with direct effect over and above the UK domestic law.
Also, Scotland Act 1988 has devolved power away from Westminster, slightly moving the UK toward having a more flexible constitution.
However, in practice, the process of putting a Bill through Parliament is a lengthy procedure, adding the social and political considerations in case of introducing or amending an Act that has a special nature or political extension, make the UK constitution less flexible than it appears.
Case law
Because the courts have broad discretion in their judgements and constantly reevaluate laws, this could be deemed as a more flexible source of the constitution than statutes.
A key mechanism by which the judiciary can impact the UK constitution is judicial review. The judicial review is a type of court proceeding in which a judge reviews the lawfulness of a decision or action made by a public body. In other words, it is a challenge in which a decision has been made.
Conventions
Those are rules which are not legally enforceable but may have a binding effect. These rules are based on common understanding between people. They can be created, changed or abolished without going through formal legal procedures.
For example:
Collective and individual ministerial responsibility;
Westminster does not legislate for the Scottish Parliament;
The Monarch will never withhold assent to a Bill, and
The Parliament meets every year.
However, some conventions are so vital that they are never likely to be changed, like the third example.
Prerogative powers
The executive mostly exercises the Crown’s prerogative powers. These powers can affect the constitution without the lengthy and complex practical procedures that Bills require. For example, the dissolving of Parliament, appointment and dismissal of ministers.
However, by leaving the EU, the EU law is not affecting the constitution as it was before.