The Supreme Court of the United Kingdom (which comprises the same judges that form the Privy Council, which hears Caribbean appeals) has held that Prime Minister Boris Johnson’s advice to the Queen to prorogue Parliament was unlawful, void and no effect (R (on the application of Miller) v The Prime Minister, Cherry v Advocate General for Scotland).

Parliamentary sittings are normally divided into sessions, usually lasting for about a year, but sometimes less and sometimes, as with the current session, much longer. Prorogation of Parliament brings the current session to an end. The next session begins, usually a short time later, with the Queen’s Speech. While Parliament is prorogued, neither House can meet, debate and pass legislation. There were two primary legal challenges in England and in Scotland, which were subsequently appealed, and led to the Supreme Court’s unprecedented decision with 11 Justices sitting. Both cases raised the same four issues, although there is some overlap between the issues:

1. Is the question of whether the Prime Minister’s advice to the Queen was lawful justiciable in a court of law?
2. If it is, by what standard is its lawfulness to be judged?
3. By that standard, was it lawful?
4. If it was not, what remedy should the court grant?

It was held that: in principle, if not always in practice, it is relatively straightforward to determine the limits of a statutory power, since the power is defined by the text of the statute. Since a prerogative power is not constituted by any document, determining its limits is less straightforward. Nevertheless, every prerogative power has its limits, and it is the function of the court to determine, when necessary, where they lie. It was held that a decision to advise Her Majesty to prorogue will be unlawful if the prorogation has the effect of frustrating or preventing, without reasonable justification, the ability of Parliament to carry out its constitutional functions as a legislature, as the body responsible for the supervision of the executive.

The Supreme Court rejected the argument that the Supreme Court should not answer the question as to whether Parliament was prorogued because to do so would be contrary to article 9 of the Bill of Rights of 1688, an Act of the Parliament of England and Wales, or the wider privileges of Parliament, relating to matters within its “exclusive cognisance”. The prorogation itself, it was argued, was “a proceeding in Parliament” which cannot be impugned or questioned in any court. The Supreme Court held that: “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. It is not something upon which the Members of Parliament can speak or vote. This court is not, therefore, precluded by article 9 or by any wider Parliamentary privilege from considering the validity of the prorogation itself.”

The Supreme Court carefully examined the steps taken by the Prime Minister and his advisors prior to the prorogation and found that:

1. This was not a normal prorogation – it prevented Parliament from carrying out its constitutional role for 5 out of 8 weeks;
2. The effect upon the fundamentals of UK democracy was “extreme”; and
3. No justification for taking action with such an extreme effect was tendered by the Prime Minister’s legal team.

It was held that: “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.” The remedy was therefore a declaration by the Supreme Court that Parliament had not in fact been prorogued at all. 

The decision is of fundamental importance in delineating the boundaries of the power of the Courts to overrule the exercise of executive power where that exercise is held to be unlawful.