2-Minute Brexit Brief: UK Supreme Court’s findings on prorogation of Parliament

On 24 September 2019, the UK Supreme Court ruled on two questions regarding an Order to prorogue the UK Parliament.

  1. was it ‘justiciable’: in other words, could the decision to prorogue be subjected to scrutiny by the courts?
  2. was it legal?

The court found:

  1. that it did have the power to rule on this question, and subsequently;
  2. went on to find that the Government’s decision to prorogue Parliament for five weeks was ‘unlawful’ – and that Parliament has not in fact been prorogued.

This Insight will look at the remedies granted in terms of next steps for Parliament – and detail some the rationale behind the findings of the Court.

What followed was both Houses of Parliament sitting on the following day, Wednesday 25 September – although there was no ‘Prime Minister’s Questions’ as Standing Order No. 22(5) requires that at least two days’ notice be given of questions for oral answer.

As the prorogation was declared ‘null and void’, the 2017-19 parliamentary session continues. All of the Bills that fell because they had not concluded their passage through Parliament at the time of the unlawful prorogation remain live.

Parliamentary business – including: scrutiny of the entire Government programme; passing of secondary legislation; and the holding of Parliamentary Committees – continues as though the prorogation had never taken place.

As this is a historic constitutional event, we have set out some of the background detail for the record.


28 August: The prorogation came about when – at a meeting of the Privy Council – Her Majesty, by Order in Council, ordered that Parliament be prorogued. The prorogation was to take effect on a day between 9 and 12 September. Parliament was to be summoned again on 14 October for a new session. Parliament was then prorogued on 9 September by Her Majesty acting on the advice of her Prime Minister.

The prorogation was controversial. When ‘Black Rod’ came to summon the Commons to hear the Royal Commission for proroguing Parliament the Speaker, John Bercow, stated in the House: “This is not, however, a normal Prorogation. It is not typical. It is not standard. It is one of the longest for decades, and it represents, not just in the minds of many colleagues but for huge numbers of people outside an act of Executive fiat.”

Separate legal proceedings to challenge the legality of the prorogation began in the courts of England and Wales, Northern Ireland and Scotland.

The first question before the courts concerned the justiciability of the prerogative power to prorogue Parliament. That is, could the decision to prorogue be subjected to judicial scrutiny? If found to be justiciable, the second question concerned the legality of the prorogation. Finally, if the advice upon which the decision was based was deemed to be unlawful, what would that mean for the order to prorogue itself, and for the execution of that order?

There were opposing rulings from High Court of England and Wales and the Court of Session in Scotland.

11 September, the High Court of England and Wales held that the legality of the prorogation was not justiciable in a court of law. That meant that the High Court had determined the question to be beyond the scope of judicial review.

On the same day, the Court of Session in Scotland reached the opposite conclusion. It determined that the issue was justiciable. It then concluded that the decision to prorogue Parliament was motivated by an improper purpose. The Court of Session concluded that the prorogation was “unlawful and thus null and of no effect”.

The matter was referred to the UK Supreme Court which considered both High Court and Court of Session findings.

On 24 September, 11 justices the UK Supreme Court headed by its president, Baroness Hale, handed down a unanimous judgment.

  1. The Court held that the power to prorogue Parliament is a prerogative power: “a power recognised by the common law and exercised by the Crown… on advice” of the Prime Minister. The Court did not express a view on whether Her Majesty is obliged to act on that advice; and subsequently that…
  2. …‘It is impossible for us to conclude, on the evidence which has been put before us, that there was any reason – let alone a good reason – to advise Her Majesty to prorogue Parliament for five weeks, from 9th or 12th September until 14th October. We cannot speculate, in the absence of further evidence, upon what such reasons might have been. It follows that the decision was unlawful.’ [para. 61]

Detail from the Supreme Court findings. On the question of whether prorogation is ‘justiciable’:

  • The Court asserted a right to exercise supervisory jurisdiction over decisions of the executive, which was said to have ample judicial precedent. They cited the Case of Proclamations (1611) and Entick v Carrington (1765). Based on these and other precedents, the Court concluded that it is possible to determine the lawful limits of the exercise of a prerogative power to prorogue Parliament.
  • ‘Parliamentary sovereignty from threats posed to it by the use of the prerogative powers and in doing so have demonstrated that prerogative powers are limited by the principle of Parliamentary sovereignty.’
  • ‘The sovereignty of Parliament would, however, be undermined as the foundational principle of our constitution if the executive could, through the use of the prerogative, prevent Parliament from exercising its legislative authority for as long as it pleased.’

As a result, the Court determined that the power to prorogue cannot be unlimited and must, therefore be subject to judicial review.

Having determined that the prorogation was unlawful the Court then set out remedies. The question became: is Parliament prorogued or not?

  • The Government had argued that prorogation was a “proceeding in Parliament”. Based on the Bill of Rights 1688 proceedings in Parliament cannot be questioned in any court: this is a key element of Parliamentary privilege. The Court rejected that argument: ‘The prorogation itself takes place in the House of Lords and in the presence of Members of both Houses. But it cannot sensibly be described as a “proceeding in Parliament”. It is not a decision of either House of Parliament. Quite the contrary: it is something which is imposed upon them from outside’.

The Court concluded that Parliament has not been prorogued. However, the Court did not set out the implications of the Order. Rather the Court stated: ‘as Parliament is not prorogued, it is for Parliament to decide what to do next.’

And Parliament ‘resumed’ its session, sitting the following day at 11:30 am.