Having considered, in my first two posts in this series, the general scope and underlying agenda of the Government’s Review of judicial review and the possibility of codifying the grounds of review, I turn now to the matter of justiciability. If the Review’s terms of reference are generally sparse, what they have to say about justiciability is positively Delphic:

The review should consider in particular … [w]hether the legal principle of non-justiciability requires clarification and, if so, the identity of subjects/areas where the issue of the justiciability/non-justiciability of the exercise of a public law power and/or function could be considered by the Government.

Notwithstanding this passage’s poor drafting and resulting opaqueness, it is at least clear that the framers of the terms of reference appear to have two issues in their sights: first, clarifying — by which, we can reasonably infer, is meant narrowing — the circumstances in which matters are justiciable; and, second, seeking, through manipulation of the concept of justiciability, to place certain ‘subjects’ or ‘areas’ beyond judicial review.

It is not hard to fathom the impetus for these veiled threats to judicial scrutiny of Government, the immediate cause self-evidently being the Supreme Court’s judgment in Miller II [2019] UKSC 41, in which it was held that proroguing Parliament for no adequate reason and for an extended period at a critical phase in the Brexit process was unlawful. After the Supreme Court gave judgment in this case, the BBC reported that Government sources had accused the Court of making ‘a serious mistake in extending its reach to these political matters’, while one member of the Government is said — with a degree of hyperbole that verges on hysteria — to have described the judgment as nothing less than a ‘constitutional coup’. Doubtless Miller I [2017] UKSC 5 also forms part of the backdrop to the interest that the Government is now taking in the notion of justiciability, bearing in mind the baleful headlines that it generated, castigating judges as ‘enemies of the people’, to which the then Lord Chancellor and Justice Secretary was notably slow to respond.


Put at its simplest, whether something is justiciable is about whether a given question is suitable for judicial resolution; in turn, this depends on whether the question is one that is capable of being determined through the application of legal standards. The word ‘question’ in the previous sentence is used deliberately and advisedly. Justiciability is — or, at least, should — not about whether a case (to adopt the language of the terms of reference) is concerned with a ‘subject’ or falls within an ‘area’ that is unsuitable for judicial resolution. In the remainder of this post, I set out an defend this view, and argue that the direction of travel signalled by the Review’s terms of reference would be both retrograde and constitutionally inappropriate. I also note that if the Government really does want to tackle the judicial overreach that it perceived in Miller II, more drastic — and even more constitutionally dubious — action than ‘clarifying’ justiciability will be required.

Over time, our understanding of the concept of justiciability has evolved and has become more refined. In particular, the concept has developed from a very blunt instrument into a more surgical one that is capable of being applied with suitable exactitude. This development has occurred precisely because it has been increasingly recognised that the principle of justiciability can sensibly and appropriately be applied only to specific questions that a court is asked to resolve, as distinct from broader and more imprecise notions such as the nature of a power or the subject-area occupied by a given decision. The lessons taught by the development of the case law in relation to judicial review of prerogative power, which can be divided into three phases, are instructive.

First, and for a long time, it was considered appropriate for courts to rule only on questions about whether a prerogative power existed (and, by implication, whether its scope had been exceeded), but not on questions about whether such a power had been lawfully exercised. While judicial review was thus confined, matters of justiciability were held at bay because any question about whether a legal power exists, and whether its legal boundaries have been transgressed,is by definition a question that is suitable for judicial determination and one that can be answered by reference to legal standards. It is, in other words, the type of question that is justiciable par excellence.  

Second, however, in a series of cases culminating in the House of Lords’ pathbreaking judgment in GCHQ [1985] AC 374, it was recognised that restricting review of prerogative in this way was constitutionally inappropriate. Prerogative powers today are simply a form of executive power, and there is no good constitutional reason why, other things being equal, their exercise should not be amenable to scrutiny on public law grounds just as statutory powers are. As Lord Roskill put it in GCHQ, drawing on earlier remarks of Lord Atkin, to treat acts done under the prerogative as beyond judicial scrutiny — given that ‘all such acts are done by the sovereign on the advice of and will be carried out by the sovereign’s ministers currently in power’ — would ‘hamper the continual development of our administrative law by harking back to … the clanking of mediaeval chains of the ghosts of the past’.

However, while GCHQ was an imperative corrective to an outdated form of constitutional reverence, this significant step forward was itself accompanied by a heavy dose of deference in the form of overbroad invocation of the notion of justiciability. In this way, the Law Lords largely took away with one hand what they had just given with the other: although the exercise of prerogative powers was thenceforth in principle subject to review, review was off the table in respect of many prerogatives on the ground of justiciability. As Lord Roskill put it, ‘the making of treaties, the defence of the realm, the prerogative of mercy, the grant of honours, the dissolution of Parliament and the appointment of ministers as well as others are not, I think susceptible to judicial review because their nature and subject matter are such as not to be amenable to the judicial process’.

Here, Lord Roskill fell into basic error, as later cases acknowledged. His error was the same as that which is implicit in the present Review’s terms of reference which, like Lord Roskill, presuppose that questions of justiciability fall to be resolved at a level of general abstraction that is concerned with broad-brush matters such as the ‘nature’ and ‘subject matter’ of the power at issue. This makes no sense — or, more precisely, it conflates an empirical outcome that may sometimes occur with an underlying premise that does not inevitably generate that outcome. In other words, there are certainly some prerogative powers, such as the granting of honours, that are less likely to generate justiciable questions for courts; but this does not mean that, as a category or in conceptual terms, they are incapable of doing so. The prerogative of mercy is a case in point. Notwithstanding its inclusion in Lord Roskill’s list of non-justiciable prerogatives, judicial review has successfully occurred including on the manner-of-exercise ground of natural justice (Lewis v Attorney General of Jamaica [2001] 2 AC 50). This insight — that, irrespective of their ‘nature’ or ‘subject matter’, the exercise of prerogative power can and should be judicially reviewed when the specific question at issue is suitable for judicial resolution — forms the third phase of the development of the case law in this area.

Against this background, it is necessary to ask what, if any, scope there is for reform of the concept of justiciability is a manner that would be constitutionally legitimate. As already noted, the opaqueness of the Review’s terms of reference mean that it is unclear precisely what might lie in prospect. However, it may be helpful to sketch the possibilities by reference to the above outline of the development of the law.

In doing so, it is important to bear in mind that although the foregoing focused on justiciability as it relates to prerogative powers, the lessons that the law in that area teaches about justiciability are more broadly applicable, the general principle today being that, whatever the source of a public law power, its exercise is justiciable provided and to the extent that the question before the court is one that is suitable for judicial resolution. As far as reform is concerned, two possibilities warrant particular consideration.

Manipulating the concept of justiciability

It seems reasonably clear from the terms of reference that a possibility in contemplation is legislating to manipulate the concept of justiciability, perhaps by reinstating a list of prerogatives akin to Lord Roskill’s whose exercise the courts would be told to regard as non-justiciable. This would, in effect, reinstate the blunt form of justiciability that was on display in GCHQ and would unpick the advances made in this area in the intervening decades. Would such ‘reform’ be constitutionally legitimate?

To answer that question we need to consider exactly what it is that such legislation would prevent courts from doing. It is already the case that courts will treat a question as non-justiciable if it would require the court to deal with a matter that is unsuitable for judicial resolution because it cannot be determined by the application of appropriate legal standards. Questions about what is and is not suitable for judicial determination are today resolved by reference to constitutional principles, including the rule-of-law condition that public powers be exercised in accordance with the law and the separation of powers which both requires judicial supervision of the executive branch and insists that that supervision be undertaken in a way that avoids judicial usurpation of Government. If legislation concerning justiciability were to make any difference, it would, by definition, need to preclude courts from examining matters that are presently regarded — in the light of relevant constitutional principles — as suitable for judicial resolution.

This, in turn, would cast doubt on the constitutional legitimacy — in the sense of its compatibility with relevant constitutional standards — of legislation that sought to remove matters from the courts’ purview through artificial extension of the notion of non-justiciability. Indeed, it is fair to say that such legislation would, in effect, amount to an attempt to oust judicial review in circumstances in which it otherwise would (and should) lie, and that it therefore would (and should) attract a judicial response comparable to that which is elicited by more familiar forms of ouster (about which I wrote in my previous post in this series). What this boils down to is that dressing an ouster clause up as legislation that ‘clarifies’ the doctrine of justiciability is like putting lipstick on the proverbial pig: at the end of the day, such legislation would still amount to an attempt to displace the public law jurisdiction with which the courts are imbued by, and which they exercise in order to uphold, fundamental constitutional principles.   

Full-frontal assault

If the first possibility is constitutionally improper, a second is positively outrageous. If the Government wished to go further than attempting to clamp down on the review of certain (prerogative and/or other) powers by requiring courts to treat their exercise as non-justiciable, they might go as far as to direct that all questions pertaining to such powers, including questions as to scope, be regarded off-limits to the courts. This would mean that courts — if prepared to take such legislation at face value — would be powerless even to determine whether a given power existed and whether its legal limits had been exceeded. Of course, this would be a full-frontal attack on both the rule of law and the separation of powers, since it would undermine the foundational premise that government must occur according to law and that independent courts must be capable of ensuring that the Government possesses, and remains within the scope of, the powers under which it professes to act.

The prospect of attempting to undermine judicial review in this way and to this extent might seem so far-fetched as to be unworthy of discussion. Yet if it really is the Miller II case that lies behind the Government’s concerns in this area, it may well be necessary to go this far in order to address the perceived problem. This is so because of the way in which, in Miller II,the Supreme Court sidestepped questions about justiciability — which, as we saw in the previous section, are raised when the exercise, as distinct from the existence or scope of prerogative powers, is in question — by treating the matter before it as one going only to the scope of the power. The Court did this by holding that, before any question as to the lawfulness of the exercise of the prorogation power arises, the very scope of the power is exceeded if it is deployed to suspend Parliament without reasonable justification. By concluding that such justification was absent, the Court was able to dispose of Miller II by ruling that the scope of the prorogation prerogative had been exceeded, thereby avoiding any need to consider questions about lawfulness of exercise and, hence, justiciability.

Whether this was a legitimate approach or was, as some have suggested, a conceptual sleight of hand will be considered in another post in this series. What is, however, important for present purposes is that if the Government really does intend to put the judges ‘in their place’ following Miller II, this would necessitate a not merely legislative manipulation of the concept of justiciability — which can logically bite only on questions pertaining to the exercise of powers — but also a direct attack on the courts’ jurisdiction to determine whether the legal boundaries of a claimed governmental power have been breached. This would be such an extraordinary affront to basic constitutional principle that it is very hard to imagine a court considering it appropriate straightforwardly to apply such legislation. However, if the Government really does wish to tackle the Miller II ‘problem’, as it sees it, head-on, the Supreme Court’s reasoning in that case would leave it with little option other than to take this sort of drastic action. By reading a reasonable justification condition into the very scope of the prorogation prerogative, the Court ensured that no amount of ‘clarification’ of the notion of justiciability will displace the form of review undertaken in Miller II.

Whether the Government has the political capital to go this far, and to cause Parliament to enact the kind of legislation that would be required to overcome Miller II, remains to be seen. If that were to happen, it would also remain to be seen whether the courts would be prepared to concede that the political branches possess sufficient constitutional authority to mount such a fundamental assault on judicial review. While that issue, were it ever to become a live one, would be deeply controversial and contested, it should not — for the reasons explored in my previous post — be blithely assumed that the courts would or should capitulate merely on the ground that Parliament is sovereign. Although totemic, parliamentary sovereignty is but one feature of a constitutional order that consists of a set of interlocking fundamental principles, the relationships between which would be tested to an unprecedented degree were the political branches to launch this sort of direct assault upon the courts’ judicial review powers.