The Supreme Court has ruled unanimously that the Prime Minister's decision and advice to Her Majesty the Queen on the prorogation of Parliament were unlawful and invalid, and that Parliament has (in legal terms) not been prorogued. The judgment is very significant as regards the constitutional issue of the legal limits to prerogative powers of the Prime Minister and also in relation to Brexit and Parliamentary scrutiny of Brexit plans. The judgment shows that the government's actions to deliver a Brexit pursuant to the 2016 referendum are subject to the constitutional principles of Parliamentary sovereignty and of accountability (of the Prime Minister) to Parliament.
Parliament was purportedly prorogued by an Order in Council dated 28th August 2019 for a period of approximately five weeks starting between the 9th and 12th September and the 14th October. The Supreme Court proceedings resulted from cross-appeals by the claimant Gina Miller against the High Court's ruling of 13th September that the prorogation of Parliament was not justiciable and by the government against the ruling of the Scottish Inner Court of Session (the Scottish appeal court) of 11th September that the prorogation was unlawful. The High Court had allowed a "leap-frog" appeal direct to the Supreme Court.
The Supreme Court needed to establish three major issues: first, was the decision to prorogue Parliament justiciable (i.e. do the courts have the power to intervene or is it a purely political issue?); second, if it is justiciable, was the prorogation decision lawful; and third, what remedies (if any) are appropriate?
First question: can the courts intervene?
On the question of justiciability, the Supreme Court concluded that it is well established that the courts can rule on the extent of prerogative powers, by determining the limits of such powers as against the important constitutional principles of the sovereignty of Parliament and the accountability of the Prime Minister to Parliament. The Court's conclusion was that a decision to prorogue Parliament (or to advise the monarch to prorogue Parliament) 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 legislator and as the body responsible for supervising the executive. The principle of Parliamentary sovereignty requires that limits on the power to prorogue be observed. The Court cited historic case law dating from the Case of Proclamation of 1611 to the effect that prerogative powers are limited by statute and the common law including the country's (unwritten) constitutional principles.
The Supreme Court noted that the principle of Parliamentary accountability is not jeopardised if Parliament is prorogued for a customary short period. It then stated: "But the longer that Parliament stands prorogued, the greater the risk that responsible government may be replaced by unaccountable government: the antithesis of the democratic model." The power to prorogue is limited to what is compatible with the ability of Parliament to carry out its constitutional functions.
The lawfulness or unlawfulness of the prorogation decision
On the question of the lawfulness or unlawfulness of the exercise of the prerogative power of prorogation, the Supreme Court placed Brexit centre-stage. The first question is whether the Prime Minister's action has the effect of frustrating or preventing the constitutional role of Parliament in holding the government to account. The Court emphasised the exceptional nature of the circumstances having regard to the fundamental constitutional change due to take place with the UK's exit from the EU set for 31st October 2019. The Court observed that whilst the people have supported leaving the EU in the 2016 referendum, Parliament and in particular the House of Commons (as the democratically elected representatives of the people) has a right to have a voice in how that change comes about. Moreover, the Court observed, the House of Commons has already demonstrated that it does not support the Prime Minister on this critical issue, by means of its motions against leaving the EU without an agreement and by passing the European Union (Withdrawal) (No 2) Act 2019 (the so called anti-hard Brexit law) and that it is especially important that the Prime Minister be ready to face the House of Commons on these questions.
The next question was whether there was any reasonable justification for the Prime Minister's action, given the extreme effect that it had on the fundamentals of democracy. The Court was here not concerned with the Prime Minister's motive for his actions, but rather with whether there was an objective reason for the decision, and whether a prorogation of five weeks was needed. In this regard, evidence was provided by the former Prime Minister John Major, without being challenged. His evidence stated that only a matter of days is normally needed to put together a government's legislative agenda for a Queen's Speech, and that he had never known a government to need as much as five weeks to do so. No evidence was provided by the government in support of the length of the prorogation or as to why prorogation was needed as opposed to Parliament going into recess (as it normally does during the party conference season). There was no evidence to indicate that the Prime Minister, in giving advice to the Queen, was doing more than simply promoting the government's own policies (as opposed to exercising a constitutional responsibility). In the absence of any reason to advise the Queen to prorogue Parliament for five weeks, the decision was unlawful.
The Supreme Court's conclusions on the substance and on remedies
The Supreme Court's overall conclusion was that the Prime Minister's advice to the Queen to prorogue Parliament was unlawful and that the resulting Order in Council was likewise unlawful and of no effect. On this basis, the actual Order in Council was also unlawful and of no effect and was (in legal terms) "a blank piece of paper".
This meant that Parliament had not been prorogued, and that no further specific remedy needed to be ordered by the Court. There was therefore no need for Parliament to be recalled, and as Parliament had not voted to go into recess, it was for the Speakers of each House to take steps for each of the Houses of Parliament to resume meetings.
The conclusions that can be drawn from the Supreme Court's judgment include the following. First, it is a judgment of great significance in upholding the constitutional principles of the sovereignty of Parliament and the accountability of the Prime Minister to Parliament and (in this context) the limits on the prerogative powers exercisable by the Prime Minister. The judgment shows that, however significant the result of the 2016 Brexit referendum, the government's measures designed to fulfil the referendum result are constrained by these constitutional principles. The judgment will be seen as a landmark in the legal history of the UK's constitution.
This article is part of our Brexit series.