A beginner's guide to the UK's constitution

On the second day of the Article 50 court case, its significance for democracy in the UK is still clear. What is clear is that our unwritten constitution is creaking under the pressure of Brexit.

Inevitably, lots of constitution-speak is being thrown around. What is the Royal Prerogative and why is it important in this case? We think public interest in the court case is a great chance to talk about the UK’s chaotic unwritten constitution.

What is a constitution?

A constitution sets out the rules and principles on how a state or other organisation is governed.

A constitution sets out what different groups - MPs, Judges, voters, the government can and cannot do. It sets out the structures of governance and the powers and responsibilities which reside with each part. Constitutions are important as they place restrictions on the government of the day, preventing them from becoming too powerful or tyrannical.

The UK constitution is unwritten, or if you prefer, uncodified. This means that it isn’t written down in a single place, you can’t go to the library and take a copy. Instead we have a series of laws, precedents and conventions that make up UK constitutional law. This makes the UK constitution very complicated and we often have to rely on experts to interpret it.

Sources of the UK constitution


Constitutional law is largely made up of normal laws that have been passed through Parliament but are seen as particularly significant or important. They usually deal with the subject of assigning powers or rights, or restricting powers. They have been built upon over time, some significant ones are:

  • The Magna Carta

  • The Bill of Rights (1689)- this established the the principle that Parliament is more powerful than the King or Queen
  • The Scottish, Irish and Welsh Devolution Acts (1998)
  • The Human Rights Act (1998)


Conventions are unwritten rules, they are essentially habits that have developed over time. They are not written down in law or often even on paper, but people follow them because this is how it has been done before. They can set out how the government should act. The existence of the role of Prime Minister is a convention that has become part of UK constitutional law.

There are also many other sources such as important judgements made in the courts and international treaties. There is often tension between different parts of the constitution. One example is the Queen giving her approval to bills passed by Parliament. This is known as Royal Assent and is required to make a bill into law. Legally she has absolute and unchallengeable power to refuse to give it, but there is a very strong convention that she approves any law passed through parliament.


Parliamentary Sovereignty

The fundamental principle of the UK constitution is that Parliament is sovereign. This means that only Parliament has the power to make and unmake law. There is no law that any Parliament can make that a future Parliament cannot scrap or amend. Parliament is the supreme legal authority in the UK.

Rule of Law

The Rule of Law is the principle that the law should apply to everyone equally. No one is above the law (not even the Prime Minister) and it should always be applied.

To make sure that judges can apply the law equally to all people, they have to be independent.  They must not be influenced by the government, MPs or what the public thinks.  They should be neutral in their decision making and non-political. But politicians often criticise judges and this can threaten judicial independence.

Separation of Powers

This is the idea that the branches of government; legislature (Parliament), the executive (cabinet and civil service), and the judiciary should be independent of each other. This provides checks and balances to prevent any one part becoming too powerful. It is seen as a safeguard against tyranny and dictatorship.

The separation of powers is deeply enshrined in the US constitution but in the UK there is plenty of overlap between the branches. For example the Prime Minister is part of the executive and also part of the legislature as she sits in Parliament.


Legislature - Parliament

As Parliament is sovereign only Parliament has the power to make laws and give or take away citizen’s rights. While we are members of the EU, even European legislation is ultimately subject to UK Parliamentary approval.


In the UK the judiciary interprets laws made by Parliament and makes judgements about whether they are being followed. Unlike the US, the UK judiciary cannot overrule Parliamentary laws or declare them ‘unconstitutional’. In the current court case on Article 50 the judiciary must decide whether Theresa May’s intention to trigger Article 50 without consulting Parliament complies with constitutional law.

Executive - Royal Prerogative

Royal Prerogative powers are left over from when England was directly governed by a monarch. These powers used to be wide reaching but as England evolved into a democracy they were gradually diminished. While many Royal Prerogative powers still exist they are mainly delegated to government ministers.

The issue of Royal Prerogative powers is important because they are powers that the government can decide to use without consulting anyone else.  These powers are not scrutinised and can’t be amended or changed.

Remaining Royal Prerogative powers include: the granting of honours, the appointment as dismissal of ministers, the ownership of swans and, most importantly for the Article 50 case, the power to make and break treaties.

Devolved powers

Devolved powers are those which the UK Parliament has given to devolved parliaments. These powers are different in Scotland, Wales, and Northern Ireland but include things like power over health and education policy. However, as the UK Parliament is sovereign in theory they can take these powers away at any time.

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