The Court of Session’s decision that proroguing Parliament was unlawful

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This blog looks at the reasons given by the Court of Session for deciding that the current prorogation of the UK Parliament is unlawful.

The Court of Session ruled last Wednesday that the decision to prorogue the UK Parliament was unlawful and therefore “null and of no effect” (paragraph 60). This is in contrast to a decision in the High Court of England and Wales. There, it was held that the decision to prorogue was “non-justiciable” – in other words, not a matter which the courts could consider.

Both decisions are due to be reviewed by the UK Supreme Court. The hearing is due to start on Tuesday 17th September, but it may be several days before a decision is announced.

The constitutional framework behind the decision

The UK is often described as having a constitution of convention. This means that, rather than written rules, the UK relies on informal conventions and previous practice. These can evolve over time, making the constitution flexible. However, it has tended to mean that disputes are dealt with in the political arena rather than the courts.

The conventions of the UK constitution are intended to balance three different roles:

  • the role of the “executive” – the UK Government – to take forward its policy
  • the role of the UK Parliament to (amongst other things) hold the executive to account
  • the role of the courts to interpret and uphold the law.

Separating these roles is intended to stop too much power being exercised by one body. Each branch is held in check by the others.

Some issues are seen as properly being in the realm of politics. It is not the courts’ job to get involved in these sorts of decisions. They are described as non-justiciable. This essentially means that they are matters which should not be determined using legal principles. In the context of the current case, this would be because they are argued to be matters of political judgement which are not measurable using legal standards.

There are two further constitutional principles which set the scene for the Court of Session’s decision. These are:

  • Parliamentary sovereignty – this is the idea that the UK Parliament is the supreme legal authority in the UK, not the executive or the courts.
  • The rule of law – this concept requires that no one is above the law, including government or monarchs. It is seen as the cornerstone of a transparent and accountable political system. It requires an independent judicial system to adjudicate on rights.


Prorogation is the means by which the UK Government can bring a UK Parliamentary session to an end. The decision to prorogue is technically made by the Crown, in the form of the Queen. However, in practice, she follows advice given by the Prime Minister and Privy Council.

During prorogation, no legislation is considered, no debates are held and no parliamentary questions are answered. The decision to end a prorogation is also effectively a decision of the UK Government.

See the House of Commons Library briefing “Prorogation of Parliament” (2019) for more information on prorogation.

Prorogation differs from a parliamentary recess. The UK Parliament remains in control of its time during a recess and can chose to reconvene if circumstances justify it. The UK Parliament also agrees whether there should be a recess.

Judicial Review

The case in the Court of Session was brought as a form of legal action known as judicial review. Judicial review looks at the procedural aspects of decisions made by public bodies, as opposed to the strengths and weaknesses of the actual decision. There are three main grounds for judicial review (although there are many sub-categories). These are:

  • that the decision went beyond the legal powers of the body making it;
  • that the procedure used to reach the decision was unfair or improper, and
  • that the decision was irrational.

The SPICe briefing “Judicial Review” (2016) looks at this type of court procedure in more detail .

The Court of Session’s decision

The most recent judgment came from the Inner House of the Court of Session. This is Scotland’s most senior court for civil cases. It hears appeals from decisions of lower courts.

Here, the case was originally raised in the Outer House of the Court of Session, which considers cases for the first time. The judge in the Outer House held that the decision to prorogue was non-justiciable.

Three judges heard the Inner House case. They each issued a separate judgment, setting out a slightly different background to their decision. However, the reasons were broadly similar. The full text is available on the Scottish Courts website.

Ultimately, none of the judges thought the reasons given for the UK Government’s advice to prorogue were the real reasons

The UK Government contended that the reason for the prorogation was to bring forward the Government’s new legislative programme via a Queen’s speech. This is a standard use of the power to prorogue.

However, the judges held that this could not justify a prorogation of the length in question. In the absence of other reasons being put forward by the UK Government, they were entitled to presume that the real reason was to reduce the time available for parliamentary scrutiny at a crucial time.

Executive powers used for improper purposes were subject to judicial review

Each judge carefully considered whether the decision to prorogue was non-justiciable. They concluded that such a power, properly exercised, was a matter for the executive branch of government, and not something the courts could interfere with.

However, they also held that, in this case, the power had not been properly exercised. It was being used to restrict parliamentary scrutiny of the Brexit process. This was contrary to the generally accepted standards of behaviour of public authorities and the rule of law. On this basis, the courts were able to intervene.

In the words of Lord Drummond Young (paragraph 106):

“The courts cannot subject the actings of the executive to political scrutiny, but they can and should ensure that the body charged with performing that task, Parliament, is able to do so.”

The judgment does not appear to rest on any special points of Scots law

All three judges appear to have based their decision on the general grounds of judicial review – which are recognised in Scotland and the rest of the UK. Lord Carloway specifically stated that the decision flowed from the common law (the traditional law as developed by judges’ decisions in individual cases) and not “any speciality of Scots constitutional law” (paragraph 51).


Abigail Bremner, SPICe researcher civil justice