The Supreme Court has ruled that the Prime Minister's advice to the Queen to prorogue Parliament was unlawful. Our Head of Constitutional Affairs analyses what will come to be seen as a major landmark in the demarcation of the relationship between Parliament, the executive and the courts.

The Brexit process may not have achieved an awful lot thus far in concrete terms, but it has definitely served to bring constitutional law issues to the fore in a way not seen before.

When we look back at the constitutional issues raised by Brexit, the UK Supreme Court's judgment in the linked case of R (Miller) v the Prime Minister and Cherry and Ors v Advocate General for Scotland will be seen as a landmark. We have discussed these two case in a previous piece.

In that decision, 11 justices of the Supreme Court held that the Prime Minister's advice to Her Majesty the Queen to prorogue Parliament was not only capable of being reviewed by the Court but was also unlawful. The decision is all the more remarkable for the fact that it was unanimously reached; a show of judicial consensus that was not expected.

The Court declared the advice and the Order in Council that gave effect to it to be unlawful, null and of no effect. The result is that Parliament is not now, and never was, prorogued. As Lady Hale explained in her oral summary of the judgment at hand down, it was as if the Order in Council that had been presented to Parliament by the Royal Commissioners was merely 'a blank piece of paper'.

Justiciability

The first big question for the court was justiciability - was the Prime Minister's advice to the Queen something that the Court could examine in legal proceedings? Before these proceedings many public lawyers would have instinctively said no, and the Divisional Court in the Miller case gave a very clear and succinct summary why.

The Supreme Court first sought to draw a distinction between political questions - which it could not decide - and genuine legal questions which happened to arise in a political context. It was explained that the courts had long exercised a supervisory role over the lawfulness of the actions of the Government in this second respect. It was further noted that the Prime Minister's accountability to Parliament does not prevent the courts from exercising this supervisory function - simply because Parliament has a role in holding the Government to account, that does not mean that the Court does not have a parallel role.

So what was the legal question here? The Court answered that by drawing another distinction, between, on the one hand, questions of whether a prerogative power exists and, if so its scope, and, on the other, whether there is a legal basis to challenge a prerogative power that had been exercised within its limits.

The Court stated that the first category is clearly a legal question, and is justiciable, whereas the second may throw up questions as to justiciability.

Therefore, in order to determine whether the prorogation was justiciable, the Court had first to determine what the lawful limits of the power to prorogue Parliament were. These limits represent the legal standard by which to assess the decision, and therefore form the grounds on which it could be said to be justiciable. This could be seen as a response to the Divisional Court in Miller which had stated that the issue was non-justiciable in part because no legal criteria existed against which it could be judged.

The Court stated that 'since the power [to prorogue] is recognised by the common law, and has to be compatible with common law principles, those principles may illuminate where its boundaries lie'. So we must look to the common law, and in particular, constitutional principles to determine the scope of any particular prerogative power.

By casting the issue in terms of the scope of the power to prorogue, and tying that scope to the common law, one wonders whether the Supreme Court has opened the door for many more challenges to the use of prerogative powers framed in similar terms but drawing on other common law principles.

In this case, the Court identified two constitutional principles as being of relevance - Parliamentary sovereignty and ministerial accountability to Parliament.

The Court then went on to clarify that Parliamentary sovereignty does not only mean that the laws enacted by Parliament have supreme legal authority, but that it implies a set of related elements. This is relatively uncontroversial as the courts have previously sought to ensure that Parliament's laws are given effect in practice through access to the courts (R (UNISON) v Lord Chancellor) and not frustrated by the Government refusing to make secondary legislation (R (Fire Brigades Union) v Secretary of State for the Home Department).

However, in this case it was found that Parliamentary sovereignty also entails protecting Parliament's opportunity to make laws, with the courts ensuring that the Government cannot shut down Parliament 'for as long as it please[s]'. The necessity for a legal limit on the length of a prorogation is shown by the fact that several statutes relate to the sittings of Parliament, including most recently the Northern Ireland (Executive Formation etc) Act 2019.

However, there undoubtedly exists a power to prorogue so the Court was required to determine where the limit might lie by formulating a test for the lawfulness of any particular decision to prorogue Parliament. That test was articulated as follows -

'…[A] decision 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 legislature and as the body responsible for the supervision of the executive.'

The word 'effect' is significant in that it allows the Court to escape any need to consider the Government's motive for any particular prorogation, and in this case to examine whether the Prime Minister had in fact lied to the Queen.

Lawfulness

So it was the Court's task to determine whether the prorogation did, as a matter of fact, prevent Parliament from carrying out its functions and, if it did, whether there was a reasonable justification for this.

Equipped with that test, the Court briskly moved on to conclude that 'of course' the prorogation had had the effect of frustrating or preventing the constitutional role of Parliament, and that the length of the prorogation was not 'normal' for preparation for a Queen's Speech (that being four to six days on the evidence presented by ex-Prime Minister Sir John Major). In finding this, the Court was careful to lean heavily on the 'quite exceptional' circumstances the UK currently finds itself in, and the corresponding significance this has for Parliament's right to assert its constitutional authority.

In respect of whether a 'reasonable justification' for the abnormal length of the prorogation existed, the Court was blunt in its appraisal of the Government's pleadings, concluding that it was impossible for them to conclude that there was 'any reason - let alone a good reason' for the decision. The only reason given was to prepare for a Queen's speech and the unchallenged evidence to the Court was that it did not take anywhere near five weeks to do so.

However, one of the most surprising things in the Court's analysis of either jurisdiction or lawfulness was the absence of any discussion of the Northern Ireland (Executive Formation etc) Act 2019.

In the debates during the passing of that Act both Houses of Parliament expressly grappled with the possibility of prorogation in the lead up to the 31 October and, through amendments pushed through in the teeth of Government opposition, made provision to ensure that Parliament could not be prorogued for the entirety of that period. In other words, Parliament considered and set limits on the Prime Minister's ability to prorogue Parliament ahead of 31 October. The prorogation was framed within these limits. Indeed, Parliament could have made sure that the length of any prorogation was even more tightly constrained, but it chose not to do so.

In circumstances where Parliament explicitly legislated on the issue of prorogation, and the prorogation sought by the Prime Minister lay within the limits imposed, it would seem to be difficult to justify the Court stepping in to 'protect' Parliamentary sovereignty and ministerial accountability against a Government that had acted to undermine them.

What next?

The Court held that the advice to the Queen to prorogue Parliament was unlawful, and (surprisingly) that this meant that the Order in Council that resulted from the advice was a nullity and of no effect (rather than simply needing to be quashed).

The Court was clear that its decision means that Parliament is not now, nor ever was, prorogued. Following arrangements made by the Speaker in the Commons and the Lord Speaker in the Lords, it will resume on Wednesday 25 September with the Commons sitting from 11.30am and the Lords from 3pm.

However, Prime Minister's Questions, which usually take place on a Wednesday will not take place. This is because Standing Order No. 22(5) requires that at least two days' notice be given of questions for oral answer. In the Commons, the business of the House will begin with any urgent questions which the Speaker has decided to accept, followed by Ministerial statements. It is certain that some fairly pointed questions will be asked.

Since the prorogation has been declared null and void the 2017-19 parliamentary session continues. As a result, all Bills of the 2017 session which fell because they had not concluded their passage through Parliament at the time of the prorogation will remain live.

However, the Government may nevertheless seek to prorogue Parliament again, for a shorter time period, in order to facilitate a Queen's Speech and start a new Parliamentary session. There is certainly ample leeway provided in the Supreme Court's decision for such a lawful prorogation.

Indeed, although the Supreme Court's decision is an important one in constitutional law terms, at a wider level nothing has changed in relation to Brexit. The Labour party has declined to support an election prior to either a deal being approved or an extension to the Article 50 timeline being secured. The possibility of any such deal still seems distant and, as no extension has yet been agreed, 31 October still looms large.