On 24 September 2019, the UK Supreme Court ruled unanimously, in the case of R (Miller) v The Prime Minister and Cherry v Advocate General for Scotland  UKSC 41, that the prorogation of the UK Parliament ordered on 28 August 2019 was unlawful and therefore null and void. The prorogation had been ordered by the Queen on advice of Prime Minister Boris Johnson as part of his Brexit strategy.
Prorogation of Parliament is a standard procedure, which normally follows the end of a parliamentary session. In practice, in means that neither Houses of Parliament can meet and all bills automatically lapse. The procedure can only be ordered by the Queen herself, as part of her royal prerogatives. It takes effect when a royal proclamation issued by the Queen-in-Council is read to both Houses of Parliament. Usually, prorogation means that Parliament does not reconvene until the State Opening of Parliament.
Prime Minister Boris Johnson advised the Queen to prorogue Parliament starting from between 9 and 12 September 2019 and lasting until the State Opening of Parliament on 14 October 2019. According to the Minutes of the Cabinet meeting held by conference call on 28 August 2019, the “decision to prorogue Parliament for a Queen’s Speech was not driven by Brexit considerations: it was about pursuing an exciting and dynamic legislative programme to take forward the Government’s agenda”. However, the prorogation was generally viewed as a means of preventing Parliament from interfering with the Brexit process. First of all, the requested length of the prorogation was unusual as Parliament had not been prorogued for more than three weeks since 1979 and is typically prorogued for no more than one week. Secondly, Prime Minister Boris Johnson was determined to secure a no-deal Brexit by 31 October 2019 and this was no secret. Thirdly, by the end of August 2019, it was becoming clear that the government would lose its majority in Parliament if it were to try to force a no-deal Brexit and, therefore, Parliament was likely to stand in his way.
In fact, immediately before the prorogation entered into force, on 4 September 2019, the House of Commons passed the European Union (Withdrawal) (No 2) Bill requiring the Prime Minister to seek a Brexit extension of three months, unless by then Parliament has either approved a withdrawal agreement or approved leaving without one. The Bill then passed the House of Lord under a special procedure and received Royal Assent on 9 September 2019, therefore becoming a law.
On the announcement of prorogation, Gina Miller (the same Gina Miller who successfully brought the claim in R (Miller) v Secretary of State for Exiting the European Union  UKSC 5) launched proceedings in the High Court (in England and Wales), seeking a declaration that the Prime Minister’s advice to the Queen to prorogue Parliament was unlawful. This petition was heard by the heads of the UK judiciary (Lord Chief Justice of England and Wales, Master of the Rolls and President of the Queen’s Bench Division) on 5 September 2019. They rejected the claim on 11 September 2019 on the ground that the issue was not justiciable, i.e. was of political nature and therefore outside the Courts’ power of review. The High Court, however, granted a ‘leap-frog’ certificate allowing the appeal to be heard directly by the UK Supreme Court, bypassing the Court of Appeal.
The UK Supreme Court ruled unanimously, in the opinion written by Lady Hale and Lord Reed, that the issue was in fact justiciable as it fell under a standard supervisory jurisdiction over the lawfulness of acts of the executive. It was held that the case was essentially about the limits of the power to advise the Queen to prorogue Parliament and the Courts had jurisdiction to decide on the existence and limits of this power [paras 28-37].
Then, the Supreme Court considered what the limits of the power to advise the Queen to prorogue Parliament were. The Court held that allowing the executive branch of Government, through the use of the prerogative, to prevent Parliament from legislating for extended periods of time would undermine the doctrine of Parliamentary sovereignty, which is a cornerstone of the UK constitutional system. Furthermore, proroguing Parliament for extended periods of time also breached the principle of Parliamentary accountability, dictating that the executive was collectively responsible and accountable to Parliament. For the Court, “a decision to prorogue (or advise the monarch 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 and as the body responsible for the supervision of the executive” [paras 38-51].
In answering this question, the Supreme Court took into account that the requested prorogation:
- was not a normal prorogation in the run-up to a Queen’s Speech;
- prevented Parliament from carrying out its constitutional role for five out of the possible eight weeks between the end of the summer recess and Brexit day;
- took place in the exceptional circumstances of a huge constitutional change prompted by Brexit;
- prevented the House of Commons, as the elected representatives of the people, from having a voice in how that change comes about;
- was not justified in any reasonable manner beyond being ‘desirable’ [paras 55-60].
In those circumstances, the Court ruled that there was not “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” 2019 and therefore such prorogation was unlawful [para 61].
Interestingly, at that point, the Supreme Court turned to the question what remedy, other than a declaration of unlawfulness, was appropriate in this case. The Prime Minister argued that in case of declaring the prorogation unlawful, the Court could not issue any further relief because the prorogation was a ‘proceeding in Parliament’ and therefore immune from any Court interference under Article 9 of the Bill of Rights of 1688. However, the Court ruled that the prorogation was not a ‘proceeding in Parliament’ because, although it took place in the House of Lords chamber in the presence of members of both Houses, it was not their decision.In fact, the prorogation ended the business of Parliament – exactly what the Bill of Rights of 1688 was designed to protect against, albeit from any potential Court interference. In consequence, the Court quashed the Order in Council ordering the prorogation which means that when the Royal Commissioners walked into the House of Lords with the royal proclamation ordering the prorogation, it “was as if the Commissioners had walked into Parliament with a blank piece of paper” [paras 62-71].
Crucially, although the proceedings leading to the Supreme Court declaring the prorogation to be unlawful were triggered by a clam that the Prime Minister’s motivation to request the prorogation (i.e. to prevent Parliament from interfering with the Brexit process) was unlawful, this is not the basis for the Court’s decision. In its judgment, the Court indicated that such an issue would likely not be justiciable, but decided that this would have only been required to be ruled upon if the prorogation were declared lawful [paras 53-54]. Ultimately, it was not the Prime Minister’s motivation that doomed the prorogation, but its effect on the Parliament’s functions to legislate and to hold the executive accountable.
The case of R (Miller) v The Prime Minister and Cherry v Advocate General for Scotland  UKSC 41 is yet another (next to R (Miller) v Secretary of State for Exiting the European Union  UKSC 5) high profile constitutional case which has been prompted by Brexit. On a practical level, the case means that the UK Parliament will have a say in the Brexit process. However, beyond that, from a constitutional perspective, the case limits the powers of the executive branch of Government and illustrates how vague concepts such as the separation of powers and the democratic form of government might be used by Courts as decisive factors in adjudicating public law issues.