Public Law for Everyone

The incoming Deputy President of the Supreme Court devoted a recent lecture to a critique of my commentary on his judgment in the Spitalfields case, highlighting differences between us concerning the nature of the principle of legality. In this response to Lord Sales, I argue that underlying our disagreement are two sharply contrasting conceptions of the constitution, centring on whether parliamentary sovereignty is accorded such a dominant role as to form the prism through which everything else must ultimately be viewed.

In a previous post on this blog, I wrote critically about the Supreme Court’s decision in R (The Spitalfields Historic Building Trust) v London Borough of Tower Hamlets [2025] UKSC 11, about which I have also published a case note in the Cambridge Law Journal. Lord Sales, who gave the sole judgment in Spitalfields, devoted a recent lecture to judges at the Royal Courts of Justice to making a detailed response to my critique of Spitalfields. I am grateful to him for his constructive and thoughtful engagement with my work; this post is offered in the same spirit. In it, I argue that the approach adopted by Lord Sales in his lecture, like that taken by the Supreme Court in Spitalfields, is both doctrinally and normatively problematic. On a doctrinal level, it reflects a conception of the principle of legality that polices its boundaries unnecessarily rigidly. And on a normative level, it advances an inappropriately thin view of the constitution by according to parliamentary sovereignty such a dominant place as to obscure the independent normative value of other important aspects of the constitutional order. The direction of constitutional travel thereby implied is concerning, not least in light of the future reliance that would need to be placed on domestic constitutional principle if, as is now contemplated by some leading political parties, statutory and international human rights protections were to be removed.

The principle of legality

Spitalfields concerned an unsuccessful challenge to a planning decision. Some councillors had been ineligible to vote on it because they had not been present at an earlier meeting on the same matter. In considering the reasonableness of standing orders limiting councillors’ entitlement to vote in such circumstances, the Court held that a heightened-scrutiny approach was warranted given what Lord Sales described as ‘the importance of the democratic principle that a councillor should be able to represent their constituents and the public in the local authority’s area by voting on matters affecting them’. Nevertheless, the Court held that the standing orders were not unreasonable. Nor, the Court held, was the limitation imposed by standing orders ultra vires the enabling legislation — a conclusion for which the way was paved by the Court’s refusal to accept that the principle of legality applied.

Among the classical definitions of that principle is Lord Steyn’s in R v Secretary of State for the Home Department, ex parte Pierson [1998] AC 539:

Parliament does not legislate in a vacuum. Parliament legislates for a European liberal democracy founded on the principles and traditions of the common law. And the courts may approach legislation on this initial assumption. But this assumption only has prima facie force. It can be displaced by a clear and specific provision to the contrary.

In Spitalfields, the Supreme Court held that councillors’ entitlement to vote was incapable of activating the principle of legality, notwithstanding that that same entitlement was sufficient to engage democratic principles important enough to trigger heightened-scrutiny review. On this view, the bar for triggering the principle of legality appears to be significantly higher than that which applies to heightened-scrutiny review, thus implying a hierarchy of constitutional norms, only the most important of which can activate the principle of legality. The Court sought to justify its view that principle of legality has only a ‘narrow application’ on the ground that, once triggered, it facilitates ‘radical interpretive surgery’. In his lecture, Lord Sales develops this point by contending that applying the principle of legality involves ‘the text of the statutory rule … being changed’ by the court — a step so significant that a commensurately powerful normative justification is required, thus yielding a very tightly bounded category of norms falling with the principle of legality’s protective scope.

That argument turns on a very particular view of the interpretive process, according to which applying the principle of legality — or, it would appear to follow, any other interpretive presumption — involves modifying the text of the statute. This is presumably on the basis that statutory provisions have an inherent meaning that precedes, and is thus liable to be changed, by the interpretive process. But on a less dramatic account of the principle of legality, it simply involves the court ascribing to a statutory provision that engages a relevant constitutional norm a meaning that is consistent with that norm to the extent that it is possible to do so. On that view, no question of changing the meaning of the statutory text arises, not least because the meaning of the text is, in the first place, a phenomenon that fully crystallises as a result of, not prior to, the interpretive process. As Michael Foran has pithily explained, when the principle of legality applies, ‘the strict semantic meaning of statutory provisions is not taken to reflect the legal meaning of the provisions’ — a disjunction that is readily comprehensible once we acknowledge that ‘[l]egal meaning is constructed by reference to an existing body of law, including fundamental principles of the rule of law’ (emphasis added). Viewed thus, the principle of legality is far less exceptional than Lord Sales suggests, and the case for policing its boundaries as heavily and rigidly as he advocates is weakened.

Against taxonomical rigidity

In my earlier post on Spitalfields, I described and criticised the upshot of the approach adopted by the Supreme Court in the following terms:

[A]t least as presented in the Supreme Court’s judgment in Spitalfields, … [the] principle [of legality] appears to be conceived of in all-or-nothing, binary terms in two related senses. First, either a given right or principle is or is not important enough to trigger it. And, second, once triggered, the principle is monolithic, in the sense that we move from a position of applying no relevant interpretive presumption in respect of the relevant value to applying a very strong presumption in respect of it.

Below, I defend those arguments in the light of Lord Sales’s analysis of them. First, however, it is necessary to address a preliminary point concerning the nature and scope of my argument. Paraphrasing me, Lord Sales ascribes to me the view that a further deficiency of Spitalfields is the drawing of a binary distinction between ‘the categories of heightened-scrutiny rationality review and the principle of legality’. That is not, however, what I said. My point related to the drawing of a binary distinction not between (as Lord Sales put it) ‘the categories of heightened-scrutiny rationality review and the principle of legality’ (emphasis added) but between (as I put it in my earlier post) ‘matters that are normatively important enough to trigger heightened-scrutiny rationality review and those that trigger the potentially more far-reaching consequences inherent in the principle of legality’ (emphasis added). I went on to note that in the heightened-scrutiny review context, the courts have adopted a gradated approach, recognising degrees of normative importance that inform precisely how rigorous their scrutiny ought to be (see, eg, KP v Secretary of State for Foreign, Commonwealth and Development Affairs [2025] EWHC 370, about which I have also written). I argued that a similarly gradated approach could — and, in my view, should — be adopted in respect of the principle of legality.

That argument does not, contrary to Lord Sales’s analysis of my position, reduce to contending that ‘there is a continuum between the principle of legality and heightened-scrutiny review’. Nor, again contrary to Lord Sales’s characterisation of my position, do I contend that (as Lord Sales put it) ‘if a claimant’s argument for a modified interpretation of the statutory power by application of the principle of legality fails, it is nonetheless likely to succeed, or at least will be capable of succeeding, as an argument based on the heightened scrutiny doctrine’. However, without subscribing to such views, it is possible advocate a position more nuanced than that taken by the Supreme Court in Spitalfields. While the principle of legality and heightened-scrutiny review are doctrinally and conceptually distinct, this is without prejudice to the possibility and utility of acknowledging their points of contact. As a tool of statutory interpretation, the principle of legality can, as we will see, involve reading into statutory powers limitations whose enforcement demands substantive (heightened-scrutiny) review. And the two approaches cover (at least to some extent) the same normative ground: even on Lord Sales’s hierarchical approach, some norms will be capable of triggering both the principle of legality and heightened-scrutiny review.

Against that background, the need for a threshold in respect of the principle of legality as strict as that advocated by Lord Sales arises only if the consequences of triggering the principle of legality are conceived of in monolithic terms. Such a conception was adopted by the Supreme Court when in Spitalfields it assumed that the principle necessarily involves the performance of radical interpretive surgery on the relevant statutory provision. But just as there is no need for rigidity in respect of the trigger, neither is there a need for such rigidity in respect of the principle’s application. And in fact, as we will see, the case law clearly establishes that the principle of legality can be, and is, deployed relatively flexibly.

The polylithic nature of the principle of legality

In his lecture, Lord Sales focuses on the principle of legality as a principle of statutory interpretation that, when applied to a discretionary power, has the effect of precluding its exercise in a manner that is incompatible with the relevant constitutional norm. This is apparent from the contrast he draws between the principle of legality, as he understands it, and substantive judicial review: it is only, he says, ‘where a statutory power conferring a discretion on a public authority cannot be “read down” under the principle of legality’ that ‘an area of discretion is left intact’ upon which substantive, including heightened-scrutiny, review can bite. On this understanding of the principle of legality — which, as we will see, is only a partial one — it operates as a strict limit on vires when applied to discretionary powers. Even here, however, it does not follow that a monolithic approach is necessary or appropriate, whether in relation to the norms that can trigger the principle of legality or the effect of its application. Indeed it is clear that the case law does not support such a monolithic approach, as Jason Varuhas (‘The Principle of Legality’ [2020] CLJ 578) has observed:

It would appear there is a hierarchy of rights. The more important the right, the more resilient to statutory displacement. Whereas basic norms can generally be displaced by express words or neces- sary implication, in certain contexts the“necessary implication” limb is inapplicable given the importance of what is at stake.

Importantly, the hierarchy identified by Varuhas differs from that advocated by Lord Sales. The latter envisages (a) a hierarchical, bright-line distinction between norms that are and are not capable of triggering the principle of legality (even if they are capable of triggering heightened-scrutiny review) and (b) a hierarchically undifferentiated category of norms that are capable of triggering the principle of legality — which, on Lord Sales’s view, takes effect as a monolithic interpretive presumption of fixed strength. In fact, however, the courts clearly acknowledge that within the category of norms capable of triggering the principle of legality, some are weightier than others, and that the strength of the interpretive presumption yielded by the principle of legality can vary so as to reflect the importance of the relevant norm.

The polylithic nature of the principle of legality is apparent from cases like R (Evans) v Attorney General [2015] UKSC 21 which concerned the purported exercise by the Attorney General of a power in the Freedom of Information Act 2000 allowing executive override of judicial determinations. Rejecting the generous interpretation of the override power favoured by the government, the plurality in the Supreme Court cited two fundamental principles:

First, subject to being overruled by a higher court or (given Parliamentary supremacy) a statute, it is a basic principle that a decision of a court is binding as between the parties, and cannot be ignored or set aside by anyone, including (indeed it may fairly be said, least of all) the executive. Secondly, it is also fundamental to the rule of law that decisions and actions of the executive are, subject to necessary well established exceptions (such as declarations of war), and jealously scrutinised statutory exceptions, reviewable by the court at the suit of an interested citizen.

The plurality went on to say that the relevant provision, ‘as interpreted by the Attorney General’s argument in this case, flouts the first principle and stands the second principle on its head’. Against that background, the plurality proceeded to apply the principle of legality with a degree of enthusiasm that rendered the executive override power largely nugatory. It would be counterfactual to suggest that this amounted to a typical application of the principle of legality — a point underlined by Lord Wilson’s dissenting judgment, in which he implicitly claimed the plurality had disregarded parliamentary sovereignty by re-writing, rather than merely interpreting, the relevant provision. Whether that criticism was a fair one is irrelevant for present purposes. Rather, the point is that Evans clearly demonstrates that the principle of legality does not imply a uniform approach, and that, where the underlying norm is especially fundamental, it can involve the application of presumption of such strength as to engage the very limits of what is possible within the confines of parliamentary sovereignty. It follows that Lord Sales’s argument that ‘for the principle of legality to apply it is important to identify an interpretive presumption of “preordained strength”’ cannot be reconciled with the case law. Far from applying a presumption of preordained, or uniform, strength, the weight of the interpretive presumption can, should and does vary according to the normative gravity of that which is placed in jeopardy by the relevant statutory provision.

What does, or should, this mean for the prior issue of whether a norm is capable of triggering the principle of legality in the first place? Clearly, not all norms ought to be capable of doing so: a line must be drawn somewhere. But once it is recognised that the consequences of treating a norm as capable of triggering the principle of legality are not monolithic, the rigidity of the approach in Spitalfields becomes hard to justify. Even if we accept Lord Sales’s characterisation of the principle of legality, according to which it involves — by ‘changing’ the statutory text — imposing ‘constraints upon valid parliamentary action’, and even if we agree with him that there must be a correspondingly strong justification for such judicial action, it does not follow that there cannot be a range of potential justifications — consisting of relevant constitutional norms — some of which are more compelling than others, and which in turn justify interpretive presumptions of differing degrees of strength.

Similarly problematic is Lord Sales’s argument that the strictly limited approach to the principle of legality adopted in Spitalfields is justified because (a) Parliament typically legislates by way of ‘bright-line rules’, (b) the principle of legality involves the ‘modification’ of legislation, and (c) such modification therefore ought itself to be ‘relatively bright-line in effect, to avoid the impression that the court is just making something up’. He illustrates this point by saying that:

It is not often plausible to take a bright-line statutory provision and then construe it as only applying if the relevant party (say, the executive) can justify its application. Either it applies or, because of the operation of the principle of legality, it doesn’t.

There are two difficulties with this analysis. First, as we will see below, there are many cases in which the effect of the principle of legality is to prohibit given administrative action unless it can be justified: in other words, the principle of legality involves the reading into the statute of a limitation that is not bright-line in nature. Second, it is difficult to see in what sense many of the statutory provisions upon which the principle of legality has operated in decided cases are ‘bright-line’ provisions in the first place. Indeed, many such provisions are generally worded discretionary powers. Take, for example, provisions considered in the cases discussed below such as ‘The Secretary of State may make rules for the regulation and management of prisons’ and ‘The Secretary of State may … release on licence a life prisoner who is not a discretionary life prisoner’. Such provisions, far from establishing bright-line rules, confer discretionary powers that are defined highly imprecisely. However, that (rightly) has not deterred courts from applying the principle of legality to them.

Parliamentary intention

Lord Sales’s approach to the principle of legality appears to be driven by two considerations. The first, already touched upon above, relates to his view that the application of the principle involves the ‘modification’ of statutory provisions — a view that presupposes legislation to have meaning independent of the interpretive process, and which thus treats the principle of legality as a form of exceptional judicial intervention that must be reserved for a very limited range of circumstances. That view is not, by any means, a universally accepted one, and is strongly repudiated by leading constitutional theorists including Trevor Allan (see, eg, The Sovereignty of Law: Freedom, Constitution and Common Law (Oxford: OUP, 2013).

The second consideration pertains to Lord Sales’s stance on the relevance of parliamentary intention to the principle of legality. Here, of interest is a pair of articles published by the Statute Law Review in 2019, respectively written by Robert French — former Chief Justice of the High Court of Australia — and Lord Sales. In his article, Lord Sales makes it clear that the principle of legality is ultimately about giving effect to parliamentary intention. Taking issue with Chief Justice French’s more constitutionalist approach, Lord Sales (‘Legislative Intention, Interpretation, and the Principle of Legality’ (2019) 40 Statute Law Review 53) wrote:

[T]he principle of legality is properly to be viewed as an aspect of legislative intent. It [therefore] becomes highly relevant to ask whether any supposed fundamental ‘right’, which is to be capable of modifying the meaning of legislation, can plausibly be taken to have had such a level of acceptance among parliamentarians (and as may be evidenced by acceptance by other key constitutional actors, such as senior civil servants) as to form part of the legislative context in which they meant to act.

This account of the constitution is a narrow or ‘thin’ one, portraying the constitution as the product, at least primarily, of Parliament’s will. In contrast, French’s ‘thicker’ account is readier to acknowledge that the rights and values given effect via the principle of legality have normative and constitutional weight independent of that which derives from any legislative intention that is brought to bear upon them. Thus, in his recent lecture responding to my earlier post, Lord Sales, principally relying upon his own publications as authority, sets out several criteria that must be met in order for the principle of legality to apply. Echoing his 2019 Statute Law Review article, he argues that one of the relevant criteria is that

the constitutional principle must be one which is so clear as to be taken to be recognised by Parliament itself, so that it is plausible to maintain that Parliament legislated on the unspoken assumption that the statute was to be taken to be modified by the principle — which is the basic theory underlying the principle of legality.

Far from being an uncontentious aspect of ‘the basic theory’, this is a radical claim that transforms the principle of legality into an essentially empirical construct that double counts parliamentary intention. On Lord Sales’s analysis, such intention appears to be relevant not only to the question whether legislation is expressed clearly enough to override a relevant norm, but also to the prior question whether a relevant norm deserves to be treated as capable of triggering the principle of legality. As well as presenting a notably thin view of the constitution in normative terms, this approach would risk creating significant practical difficulties. It is, for instance, unclear how a court should go about deciding whether a given norm has a sufficient degree of ‘acceptance among parliamentarians’ to warrant protection via the principle of legality — although, on the basis of existing authority, it seems that legislation would not form such evidence. In [Moohan v Lord Advocate]() [2014] UKSC 67, the Supreme Court took it as read that if Parliament consistently accords effect to a given right, the effect is to undermine the possibility of the right being recognised at common law and thereby triggering the principle of legality. If, therefore, the principle of legality is now to turn upon whether (in Lord Sales’s words) the relevant norm ‘can plausibly be taken to have had such a level of acceptance among parliamentarians … as to form part of the legislative context in which they meant to act’, such acceptance is presumably to be judicially divined from sources other than legislation. The resulting uncertainty, however, would create precisely the risk — namely, ‘the impression that the court is just making something up’ — that Lord Sales professes himself to keen to avoid.

Even if those points are left to one side, the difficulties arising from Lord Sales’s reconceptualisation of the principle of legality as an ultimately empirical construct do not end there. Imagine, for instance, a future scenario in which Parliament was controlled by a majority populist or authoritarian government that had made abundantly clear its determination to immunise large swathes of administrative action from all judicial oversight. A court that was faced with legislation that appeared to oust judicial review would presumably be forced to conclude that the principle of legality was not displaced by sufficiently clear legislation, but that the principle of legality was inapplicable in the first place because it would no longer be plausible to take as read Parliament’s general acquiescence in the constitutional fundamentality of judicial review. Indeed, on Lord Sales’s account, it is unclear how, for example, the constitutional requirement that administrative action should be subject to judicial review could ever have acquired a status sufficient to warrant protection via the principle of legality. Given the relative regularity with which Parliament has been willing to deploy ouster clauses, is it ‘plausible’ to assume that the constitutional imperative of judicial review has the requisite level of acceptance among parliamentarians for it fall within the protective scope of the principle of legality?

Lord Sales’s account of the principle of legality contrasts sharply with the accounts offered by leading cases. In R v Secretary of State for the Home Department, ex parte Pierson [1998] AC 539, invoking Dicey’s language of the ‘spirit of legality’ — which itself contrasts sharply with an approach by Lord Sales so prescriptive as to arguably move us from a spirit or principle of legality to a rule — Lord Steyn said that it is the principle of legality that provides the ‘intellectual justification’ for the famous dictum of Byles J in Cooper v Wandsworth Board of Works (1863) 14 CB (NS) 180 that ‘although there are no positive words in a statute requiring that a party shall be heard, yet the justice of the common law will supply the omission’ (emphasis added). Lord Steyn went on to say that ‘[u]nless there is the clearest provision to the contrary, Parliament must be presumed not to legislate contrary to the rule of law’. On this account of the principle of legality, the norms to which it offers protection exist independently of the sort of presumed parliamentary will upon which Lord Sales’s account is founded. Rooted in the common law, or the rule of law, it is the inherent normative value of relevant norms that justifies the presumption which the principle of legality brings into play. Similarly, Lord Hoffmann in R v Secretary of State for the Home Department, ex parte Simms [2000] 2 AC 115 rooted the principle of legality in the importance of the norms it protects, concluding that via the principle of legality, the courts, ‘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’. This aligns with the analysis of Laws J in R v Lord Chancellor, ex parte Witham [1998] QB 575, who articulated a notion of constitutional rights — mediated through the principle of legality — that are ‘creatures of the common law’ that ‘cannot be abrogated by the state save by specific provision in an Act of Parliament’.

Viewed in this way, the principle of legality is a means by which courts bring relevant aspects of the common law constitution into relationship with statutory provisions, recognising the independent normative value of the former while also acknowledging the capacity of Parliament, provided it makes its intention sufficiently clear, to override relevant common law norms. Ultimately, Lord Sales’s approach seems to me to conflate two matters. It is one thing to say that parliamentary sovereignty, at least on an orthodox understanding of that principle, means that Parliament must capable of overriding (other) fundamental constitutional norms through the use of sufficiently clear language. But it is another thing entirely to treat parliamentary sovereignty as a principle so dominant that it must form the prism through which everything else is viewed, thereby reducing the scope of the principle of legality to those norms whose fundamentality Parliament is taken to accept. The former is plainly essential if parliamentary sovereignty it to be fully acknowledged in its traditional sense. The latter manifestly is not.

Heightened scrutiny as a form of legality review

Part of the case Lord Sales seeks to build in favour of strictly limiting the scope of the principle of legality lies in his argument that that principle — because it is interpretative in nature and thus, on his account, can modify statutory texts — must operate in a bright-line manner. This point is advanced firmly and reiterated at a number of points in Lord Sales’s lecture. For instance, he argues that it is ‘not often plausible to take a bright-line statutory provision and then construe it as only applying if the relevant party (say, the executive) can justify its application’, later underlining that point by saying that ‘to read into a clear statutory power that it can only be exercised to the extent that it is justified to do so (eg according to a principle of proportionality, as in Miller II in relation to a prerogative power) looks very close to the court making up a constraint as it goes along, because it happens to think it’s a good idea’. Hence:

The operation of the principle of legality should reflect the strong normative imperative to read a statutory provision in a particular way, which is ordinarily to disapply general words rather than to change them into a rule which is not bright-line in form.

But in many cases when the principle of legality applies, it does so not by imposing a hard vires limit, but by yielding interpretations of statutory provisions conferring discretionary powers that render the use of such powers lawful only to the extent that interference with the relevant constitutional norm can be justified. Take, for example, R v Secretary of State for the Home Department, ex parte Leech [1994] QB 198, which concerned the lawfulness of a prison rule facilitating interference with prisoners’ legally privileged correspondence. Although Steyn LJ clearly considered the matter in terms of vires — ‘The question is whether section 47 [of the Prison Act 1952] by necessary implication authorises the making of a rule of the width and scope of [the contested rule]’ — the vires limit that was read into section 47 was to the effect that it extended to authorising rules interfering with privileged correspondence only to the minimum extent necessary. This, in turn, unlocked the door to a form of substantive review of the exercise of the rule-making power that went beyond the Wednesbury approach: not every rule that impeded legal professional privilege would be ultra vires, but nor would every reasonable rule that did so withstand scrutiny. Rather, an intermediate standard, amounting to a form of heightened-scrutiny review, applied, requiring judicial evaluation of questions of necessity as distinct from reasonableness. Importantly for present purposes, it was the principle of legality — which served to facilitate the construction of the relevant statutory provision so as to impose necessity-based limits on administrative rule-making — that formed the gateway to such review.

Similarly, R (Daly) v Secretary of State for the Home Department [2001] UKHL 26, another case concerning privileged correspondence, involved a vires limit being read into relevant legislation under the principle of legality — but, again, not every interference with the relevant right was thereby rendered unlawful. Rather, the effect of the House of Lords’ interpretation of the legislation was that only proportionate interferences would be lawful. As in Leech, the interpretive principle of legality involved reading into the statute not a hard vires limit but a qualified limit, the effect of which was to facilitate a form of substantive review going beyond the conventional Wednesbury standard.

As these judgment demonstrate, it is not the case that the principle of legality operates only in bright-line terms. Its effect is often much more subtle, involving not the reading down of statutory provisions but reading into them conditions for the exercise of administrative power such that encroachment upon the relevant constitutional norm must be justified if it is to be lawful. In this way, the principle of legality can open the door to heightened-scrutiny review. This does not mean that the principle of legality and heightened-scrutiny review are indistinct or even that they are on a ‘continuum’. One is a principle of statutory interpretation while the other is a form of substantive judicial review of the exercise of discretionary power. That point is uncontroversial. The more difficult question is what, exactly, turns on it. For Lord Sales, the answer is as follows:

[T]he principle of legality is a type of constraint on what Parliament can do. It operates as a type of manner and form constraint: if Parliament wishes to legislate contrary to a constitutional right or principle, it must do so in clear terms. The principle of heightened scrutiny is a constraint on what the executive (or other public authorities) can do. A basic application of principles of the separation of powers under the UK’s constitution suggests that the latter will be much easier to justify normatively than the former. That normative difference itself suggests that there should be a significant normative gap between the two doctrines and their effect. The authority of a court to identify constraints on executive action is well recognised and justified in administrative law. It is not at all the same thing for a court to introduce constraints upon valid parliamentary action.

The sustainability of this view turns in part upon how we under the constitutional basis of judicial review. If, like Lord Sales (see ‘Rationality proportionality and the development of the law’ (2013) 129 Law Quarterly Review 223), one subscribes to a theory of judicial review that conceptually regards the grounds of review as reflections of the statutorily-prescribed limits of administrative power, the distinction between the interpretive principle of legality and substantive review (or indeed any form of review) collapses. On such a view — which I share: indeed, in the article quoted above, Lord Sales endorses the ‘modified ultra vires theory’ that I set out in The Constitutional Foundations of Judicial Review (Oxford: Hart Publishing 2000) — judicial review and statutory interpretation, set within its proper constitutional context, are two sides of the same coin. Indeed, on this account of judicial review, it is the principle of legality that facilitates judicial review generally, by enabling courts to treat the grounds of review as interpretive constructs that determine the limits of the vires of those who wield statutory power. It follows, contrary to the view advanced in Lord Sales’s recent lecture, that a bright-line distinction cannot be maintained, on separation of powers or any other grounds, between (a)(a) statutory interpretation pursuant to the principle of legality and (b) the identification of constraints on executive action. Rather, the latter flows directly from the former, undermining any attempt to ring-fence the principle of legality and thereby to police its perimeter in the manner and to the degree advocated by Lord Sales.

Two views of the constitution

Ultimately, it seems to me that two views of the constitution — and of the relationship between Parliament and the courts — are in play here. Lord Sales’s analysis in his recent lecture is replete with bright lines and categories that do not fully map onto reality. (Or, perhaps more accurately, onto the reality of what has been established judicial practice until recently: a qualification that is needed given the conservative turn of the last few years in the Supreme Court’s public law jurisprudence, of which Spitalfields is only one example.) Thus, on Lord Sales’s account, the principle of legality and substantive judicial review are presented as wholly distinct — yet, in reality, there are important points of contact. Those norms that are capable of triggering the principle of legality (which are rigidly demarcated from lesser norms capable only of triggering heightened-scrutiny review) are lumped together in a single, undifferentiated category — whereas in fact not all constitutional norms are equal, and courts can and do recognise variation within the category of norms capable of triggering the principle of legality. Meanwhile, the principle of legality, once applied, is taken to operate on the basis of an interpretive presumption of uniform, preordained strength — but really the courts’ willingness to perform interpretive ‘surgery’ on legislation varies considerably depending on the strength of the underlying norm.

In each case, the latter, less categorical analysis seems to me better aligned with the case law and a better reflection of a constitutional order that defies the sort of taxonomical rigidity that Lord Sales seeks to invoke. The rejection of categorical rigidity does not, however, imply an unprincipled approach, and I do not accept Lord Sales’s charge that my preferred approach reduces to an ‘instinctive, free-wheeling one’. Indeed, the prescriptiveness of Lord Sales’s framework itself risks leaving insufficient scope for genuine engagement with constitutional principle. It is through precisely such engagement that courts have traditionally sought to identify those constitutional rights and values that are sufficiently fundamental to warrant the protection afforded by the principle of legality. Lord Sales, however, would replace such principled constitutional analysis with a principle of legality, refashioned in empirical terms, that turns upon judicial divination of whether a given norm enjoys sufficient support among parliamentarians. It is difficult to see how this recasting of the principle of legality does not ultimately undermine the rule of law itself if, in the final analysis, the only constitutional norms that can be interpretively upheld are the ones that judges think legislators support.

The constitutional vision presented in Lord Sales’s lecture prioritises parliamentary intention to an extent that goes beyond the requirements that flow from parliamentary sovereignty. The principle of legality, properly understood, reveals the richness of a constitutional order in which the legitimacy of constitutional rights and values is independently derived from their own normative fundamentality, even if their practical effect remains contingent on a process of statutory interpretation that acknowledges parliamentary sovereignty. In his 2019 Statute Law Review piece, Lord Sales seeks to justify his Parliament-centric conception of the principle of legality by arguing that: ‘An appeal to constitutional principle on its own is not sufficient because the notion of legislative intent is at the heart of a democratic constitution.’ That, it seems to me, captures the essential fault-line in this debate — between those who view parliamentary sovereignty in terms so domineering as to obscure the independent legitimacy of other aspects of the constitution, and those who see parliamentary sovereignty as one part of a rich constitutional tapestry.

Lord Sales concludes his critique of my analysis by saying:

I would characterise my approach, by contrast with Professor Elliott’s, as one which involves “Taking Statutes Seriously”.

I would characterise my own approach as one that involves taking the constitution seriously. That does not mean that Parliament, or the statutes it enacts, should not be taken seriously: but it does require that we acknowledge, to an extent significantly greater than Lord Sales’s approach permits, the other normative aspects of the constitutional framework. The courts’ stance on these issues is likely to assume ever greater importance in the coming years as possibilities such as repeal of the Human Rights Act 1998 and withdrawal from the European Convention on Human Rights are confronted. Should such developments occur, the capacity of domestic law to fill the resulting void will be sorely tested. If the vision of the constitution presented by Lord Sales prevails, that capacity will, regrettably, prove to be severely limited.

I am very grateful to Lewis Graham, Nick Kilford, Philip Murray and Paolo Sandro for their insightful comments on an earlier draft of this post.