By advising the Queen to prorogue Parliament for 5 weeks in the run-up to arguably the most significant constitutional change in the UK in generations, the Prime Minister has thrown into sharp relief the political nature of the UK constitution, and the extent to which the Judiciary can police it. A lot has been said about whether the prorogation is unconstitutional in a political sense and unconstitutional in a vires sense, with even more debate on what this latest episode in the Brexit saga says about democracy in the UK today. I intend to steer clear of the foregoing, and instead will attempt to examine the justiciability of conventions within the UK constitution.
The political and the legal constitutions
The UK constitution is fundamentally political in nature, in that it functions mainly via parliamentary, rather than judicial or executive processes. Though each of the three branches of the State is (to varying degrees) a master of its own process, it is uncontroversial that Parliament enacts the laws that enable governance by the Executive and which in turn are enforced by the Judiciary. It therefore stands to reason that, should any conflict arise in constitutional functionality, the courts turn first to the ‘hard law’ as expressed in primary legislation. Statute law therefore arguably represents the policeable boundary for judicial intervention – as Robert Craig reminds us.
However, away from the hard edge of statute law, there exist multiple political conventions which inform constitutional functionality between the various State institutions. Sewel tells us about how Parliament interacts with the various devolved legislatures, Salisbury informs us that the unelected Lords will not wreck legislation promised in the governing party’s manifesto and before CRAG 2010, Ponsonby allowed for a parliamentary role in treaty ratification, traditionally a solely prerogative power.
In Miller v Brexit Secretary  UKSC 5, though put on a statutory footing, the Sewel convention in relation to Scotland was declared to be legally unenforceable (). The Supreme Court in Miller reinforced the point, made in multiple cases over several decades, that conventions have political consequences, whether in Parliament or at the ballot box, and not legal consequences in courts.
The nature of a convention
In the Patriation Reference  1 SCR 753, the Supreme Court of Canada adopted Sir Ivor Jennings’ three-pronged test for determining whether a rule is a convention: precedent of the rule, acceptance of the rule’s binding nature and the rule’s underlying reasoning. In Miller, the UK Supreme Court endorsed the Canadian observations, together with those of the Privy Council in Madzimbamuto v Lardner-Burke  1 AC 645 and the Inner House of the Court of Session in Imperial Tobacco v Lord Advocate 2012 SC 297. However, all three of Miller’s sources agreed only that conventions are political in nature and have political consequences. In the event, Miller reached the very same conclusion.
Aileen McHarg criticises the reasoning in Miller (in relation to conventions) as being overly formalistic and inattentive to the myriad ways in which the Sewel convention could have been given legal weight without being enforced. It is difficult to argue with this criticism. By slamming the door shut on addressing the Sewel convention beyond characterising it as a political creature, the Supreme Court came up with the surprising conclusion that despite placing the convention on a statutory footing, Parliament had essentially enacted little more than gratuitous language.
But all of this raises a more fundamental question: beyond being a political norm to which certain actors feel bound, what is a convention? This goes to the heart of the third limb of Jennings’ test: reasoning. While it is impossible to find a common denominator among all conventions, some of the most important essentially answer questions going to institutional competence and capability: Sewel for example reveals a demarcation in quotidian legislative competence between Westminster and the devolved legislatures, while Salisbury speaks to a difference in capability between Parliament’s elected and unelected Houses. In the same fashion, the convention governing the Royal Assent reveals the breadth of Parliament’s competence, in that no Bill validly passed should (ordinarily) be refused Assent regardless of the Bill’s subject and the convention governing the use of the Royal Prerogative sets out the competence of an Executive which enjoys the confidence of the elected Commons, and thus democratic legitimacy.
The rule of law
Though the subject of much debate, the rule of law has never been prescribed, far less by statute. It finds perhaps its most recent authoritative analysis in the sixth Sir David Williams Lecture delivered by Lord Bingham of Cornhill in 2006. None of the statutes which governed the creation of the superior courts in any of the UK’s three legal jurisdictions mention or even touch upon the concept, and yet it is arguably the Judiciary’s raison d’être. More fundamentally, the phrase also encapsulates judicial competence: in adjudicating legal disputes, the courts must always uphold the rule of law, which has over the centuries come to be accepted as pervading the entire constitutional machinery in the UK.
While sometimes succinctly summarised as “no one is above the law”, the rule of law also requires that the law to which everyone is subject should be authoritatively declared and clarified. This judicial function, being the subject of no statute, has over the years been refined and fiercely upheld by the Judiciary as within the boundary of its own competence. In doing so, however, the Judiciary has also claimed its constitutional place as the independent arbiter of the boundaries of other institutional competences, Miller being a case in point. The competing competences of Parliament and the Executive were examined, resulting in the balance being authoritatively declared and the boundaries demarcated. The argument that Miller was merely an orthodox pronouncement on parliamentary sovereignty glosses over the constitutional function performed by the Supreme Court – that of deciding, inter alia, the respective competences of the legislative and executive branches of the State in the factual matrix of that case.
It is therefore difficult to stop at the threshold of ‘hard law’ when considering the justiciability of conventions which demarcate institutional competence. This is especially the case in a constitution which is flexible enough to change with each incoming government. Constitutional permanence and stability require that the ebb and flow of politics be tempered with some measure of legal clarity and certainty. Undeniably, there is a difference between seeking clarity and seeking enforceability as McHarg stated (above), but the inability to enforce does not equate to the inability to clarify or declare. It is at this stage worth recalling a passage in the speech of Lord Hoffmann in R v Home Secretary ex p Simms  2 AC 115:
“Parliamentary sovereignty means that Parliament can, if it chooses, legislate contrary to fundamental principles of human rights. The Human Rights Act 1998 will not detract from this power. The constraints upon its exercise by Parliament are ultimately political, not legal. But the principle of legality means that Parliament must squarely confront what it is doing and accept the political cost. Fundamental rights cannot be overridden by general or ambiguous words. This is because there is too great a risk that the full implications of their unqualified meaning may have passed unnoticed in the democratic process. In the absence of express language or necessary implication to the contrary, the courts therefore presume that even the most general words were intended to be subject to the basic rights of the individual. In this way the courts of the United Kingdom, though acknowledging the sovereignty of Parliament, apply principles of constitutionality little different from those which exist in countries where the power of the legislature is expressly limited by a constitutional document. (emphasis added)”
The above commentary applies equally to questions of institutional competence, answered by conventions, the clarity of which is sought from the courts. The risk that the unqualified meaning of a political convention muzzles an institution and strips it of capacity in a bid to uphold or assert the democratic process is not quite chimeric. Indeed, courts have been willing to answer similar questions in other fields. The long-standing rule of treaty justiciability, for example, in which an unincorporated treaty cannot give rise to domestic obligations (see JH Rayner Ltd. v Department of Trade and Industry  2 AC 418) nevertheless gives way to circumstances in which such a treaty could influence the development of domestic law (see R(SG) v Work and Pensions Secretary  UKSC 16). Though this can be explained by reference to the legal fiction that Parliament does not intend to legislate in a way contrary to the UK’s international obligations (see e.g. Garland v British Rail Engineering Ltd.  2 AC 751), the fiction is indicative of the judicial understanding of Parliament’s legislative competence while appreciating the limits of enforceability: that Parliament will not ordinarily act to breach international obligations, but it shall squarely confront the political cost of doing so should it so choose.
This brings me back to the start of this post and the Prime Minister’s advice to the Queen on prorogation. Prorogation, being an exercise of the Royal Prerogative, is governed by the convention that the Queen (generally) exercises prerogative powers on the advice of her government. The circumstances of this prorogation have divided commentators and the timing and speed at which the advice was tendered, and the consequent Order in Council made have invited questions of motive and purpose. Whatever the precise motive or purpose behind the advice, the competence of the Prime Minister to tender such advice, in all its surrounding circumstances, is a question which the courts should answer, in keeping with the role of the Judiciary as the authoritative arbiter of law and constitutional principles. If the answer goes against the Prime Minister, he must squarely confront the political consequences. However, whether or not there will be such consequences depends very much on the courts’ ability and willingness to adjudicate on the functioning of the convention at issue.
In Miller, the Supreme Court had declared, “Judges […] are neither the parents nor the guardians of political conventions; they are merely observers” (). Judges may well be observers, but they are not required to be silent.
The case for the prorogation advice having been given for an improper purpose has been made, most recently and powerfully, by Paul Craig, while Sir Stephen Sedley has also identified compelling reasons why the consequent Order in Council might be unlawful. I only add that whatever the outcome of the substantive arguments, the respective courts should embrace their roles as arbiters of the constitution, engaging with and adjudicating on these arguments.
The complexity and controversy which may follow the judicial examination of conventions do not detract from the need to provide clarity in the increasingly fraught debate on the substance of the constitution. The lack of legal enforceability should not render the UK constitution one of straw.
Anurag Deb is a Paralegal at KRW LAW LLP and a BPTC graduate of The University of Law