II. Basic elements

The central thrust of Kant’s constitutional theory is to explicate the necessary constraints that individuals and states must accept if they are to fulfil their obligation to leave the ‘lawless state of nature’, and to enter into a ‘Rightful’ civil condition. They must do so to secure their own freedom in community. Two principles are foundational, in that they constrain the construction of the system. The Internal Duty of Rightful Honour prohibits one from consenting to social arrangements that would permit one to be used as a mere means for others (MM 6: 236). And the Universal Principle of Right [UPR] limits ‘authorization to coerce’ to those acts that meet the demands of Right (MM 6: 230–1). Kant defined Right as ‘the sum of the conditions under which the choice of one can be united with the choice of another in accordance with a universal law of freedom’ (MM 6: 230). He conceptualised the civil version of Right as an inherently constitutional order:

All rational beings are required to set and pursue ends in light of the freedom of every other rational being, and they may not withhold their consent from law that conforms to the UPR. Public law constitutes the civil condition, on which every person’s external freedom constitutively depends (MM 6: 316; Zylberman Reference Zylberman2016). The state – a set of linked, ‘omnilateral’ organs through which officials make, interpret, and enforce law, as agents of the sovereign People (MM 6: 313–18) – is authorised to coerce individuals for the purpose of realising Right, but coercion is forbidden for any other purpose (MM 6: 231).

Box 1 contains selected commentary by Kant on these and other core concepts, the implications of which we discuss in each of the sections to come. We begin where Kant does, with the concept of freedom.

III. Freedom and rightful coercion

Kant argues that external freedom – ‘independence from being constrained by another’s choice’ is ‘the only one innate right’, possessed by ‘every man by virtue of his humanity’ (MM 6: 237). The scope of freedom is subject to the UPR: the external independence of any person is to be recognised ‘only insofar as it can coexist with the freedom of every other in accordance with a universal law’ (MM 6: 237–8). Freedom is innate in that its existence does not depend on any affirmative act on the part of an agent or the state, unlike the ‘acquired rights’ that form the substance of contract and property law, for example. Kant supposes that a person’s means-based capacity is conceptually prior to the setting of ends. In the absence of such capacity, one can only wish for an end; but one cannot make it one’s purpose to set about achieving that end. It follows that every person must possess certain inherent powers if they are to be, in fact, independent.

Independence is a relational concept; as Ripstein stresses, it ‘cannot be predicated of a particular person considered in isolation’ (Ripstein Reference Ripstein2009: 15). A person is independent only if she is able to exercise her capacity to set and pursue ends without being subject to the controlling authority or influence of another person (Hodgson Reference Hodgson2010: 793; Zylberman Reference Zylberman2016: 109). Independence is also counterfactually robust: person X is not independent from Y, if Y has a power to interfere with X’s capacity to choose, even if Y foregoes the exercise of that power. Slaves whose master declines to interfere with their decisional autonomy are nonetheless subject to the master’s relational authority, since the master could exercise it. On Kant’s view of freedom, actual non-interference is neither a necessary nor sufficient condition for freedom. Indeed, non-interference can coexist with another person’s entitlement to interfere, as in the case of the benign slaveholder. More important for our purposes, Kant stipulates that coercive interference with the independence of each person is defensible only when it is necessary to secure the freedom of all in a Rightful, legal order.

Innate Right begets the principle of Rightful Honour, which is expressed through the maxim: one may not allow oneself to be used as a mere means for others (MM 6: 236). At first glance, this requirement looks out of place in the Doctrine of Public Right, which concerns social interactions and arrangements. But the internal duty of Rightful Honour is also relational: it operates to restrict a person’s exercise of freedom, by barring them from entering into legal relationships that are inconsistent with their own status as free and equal persons (also Ripstein (2009: 37). Reciprocal relations among free persons must respect the Innate Freedom – one’s inalienable, means-based capacity – not undermine or destroy it.

The notion of freedom as an innate attribute of personhood means that all individuals are entitled to pursue their chosen ends, so long as they do not violate Rightful Honour along the way. We can, on these grounds, distinguish freedom from other justifications of coercive public authority, including welfare maximisation. An agent may always ask – why should I accept that reason for coercion? The Kantian response is stark and unyielding: the only acceptable justification for restricting the freedom of a rational agent is the need to instantiate the collective freedom of everyone (MM 6: 316).

Thus, considered in terms of institutional design, Rightful Honour restricts the delegation of certain legislative powers to state organs, thereby constituting a micro-foundation of the Rightful civil condition itself. And the UPR constrains how officials are to fulfil to exercise their powers to make, and coercively enforce, the law. State coercion to promote an end other than the construction of Public Right is categorically forbidden, no matter how worthwhile that end might seem to be, or how many might value it.

Looking forward, what are the structural implications of these arguments for contemporary constitutional law and practice? First, the principle of Rightful Honour means that no person may justifiably accept any binding arrangement that abrogates her basic entitlements to freedom (see Zylberman Reference Zylberman, Follesdal and Maliks2015). Put positively, in a Rightful constitutional condition, every person possesses an inalienable entitlement to justiciable rights. Second, public law constitutes the external freedom of all. As elaborated further below, a charter of rights does not merely give concrete expression to freedom, but grounds the construction of the Rightful constitutional condition. Third, in any Rightful condition, a person’s independence is subject to justifiable limitations. Kant, after all, connects the UPR to a public lawmaker’s ‘authorization to coerce’ at the outset of the Doctrine of Right (MM 6: 230–1). Public law articulates the scope and content of each person’s external freedom to act purposively within society, insofar as that law meets the demands of the UPR. Rights authorise officials ‘to hinder any hindrance’ to freedom (MM 6: 231), in order to realise the external freedom of all under a system of law.

IV. The state and omnilateral law-making

Suppose that two persons, X and Y, attempt to interact on conditions of equal freedom in the absence of authoritative legal institutions. If X makes any territorial claim – even through moving from point A to point B – the effect of X’s action will be to place Y under an implied duty: to refrain from moving to point B or otherwise interfering with X’s purpose for doing so.^{Footnote 5} By what authority does X impose this obligation on Y? Prior to X’s decision to walk from point A to point B, Y enjoyed an equal entitlement to move to point B. X’s move eviscerates Y’s entitlement, while impliedly shackling Y with new obligations. Given the principles of Rightful Honour, X could not possess the capacity to unilaterally subjugate Y’s freedom to X’s purposes. Y may not allow the private will of X to determine Y’s purposes. Self-abnegating deference to the unilateral determinations of others conflicts, more generally, with the dictates of independence and of Rightful Honour. Simplifying a complex argument, even when people do succeed in freely negotiating rules to govern their relations, these arrangements can only be provisional. In a pre-legal condition, Kant famously insisted (MM 6: 256–317), binding legal entitlements cannot exist, because no private person has a power to bind another to act in accordance with duties of Right.

The dilemma Kant diagnoses is one of unilateral authorisation: Y is never required to accept X’s attempts to assert, unilaterally, any entitlement that would limit Y’s freedom. X possesses no legitimate authority to compel Y to do anything. The solution requires delegation of powers to an omnilateral lawgiver – an institution with public authority – to create a Rightful condition (MM 6: 263). Public acts are omnilateral insofar as they are choices taken on behalf of all citizens, rather than the choices of one or a group of particular persons. Omnilateral acts are those that seek to create or preserve the formal conditions under which persons can rule themselves, that is, to be externally free in community, under the UPR (MM 6: 263).

Omnilateral lawmakers establish determinate boundaries on the zone of freedom in which individuals interact. At the same time, the UPR constrains the exercise of public authority (see also Ripstein Reference Ripstein2009: 145–81). Thus, with respect to tensions that may result from a territorial clash between X and Y, the omnilateral state regulates. The law may: (i) demarcate the spatial zones in which X and Y may act without being liable in trespass; (ii) enforce a rule of first-in-time for occupancy; (iii) establish conditions for claiming title; or (iv) turn the land into a public park. Officials can realise Public Right through myriad means. It is crucial, however, to stress that omnilateral law-making has the inherent capacity to construct a new normative condition that can not be fully comprehended in terms of a priori moral reasoning; only the principles of Public Right, which are given content through law-making, can be known a priori. Thus, nothing in Kantian theory tells us what types of meanings people may invest in a public park, or how such meanings may influence subsequent disputing about its use.

Tellingly, Kant defines the state as ‘a union of a multitude of human beings under laws of Right’, whose legislative powers ‘can belong only to the united will of the People’ (MM 6: 313). He characterises deputies in parliament as both representatives of the People, and ‘the guardians of its freedom and rights’ (MM 6: 319). The next step comes naturally: all state officials, agents of the people, are under a duty to make, interpret, and apply law in a manner consistent with the UPR. While we will specify these duties with more precision below, at this point it is enough to repeat that the delegation of law-making authority is a functional necessity, given the incapacity of individuals to realise Public Right on their own.

V. Rights as positive requirements of legality

What little Kant tells us about delegation and the creation of the state is filtered through the idea of the original contract:

Kant characterised the ‘idea’ as a necessary theoretical construct; it does not depend upon the facts of how any state actually emerged or operates. The construct contrasts with classical contractarian accounts of political authority, which link the legitimacy of state coercion to a datable act of voluntary agreement or authorisation in which persons cede powers to the state. Presupposing the original contract sets the stage for an elucidation of the demands imposed by the UPR on the exercise of public authority.

Kant wrote before any state, as he defined it above, had ever been established. He was also silent on many crucial issues of constitutional design. He did not develop a full-fledged theory of rights, or specify the mechanisms for their protection. Kant illustrates his arguments with reference to a small handful of rights; and he provides little guidance to a polity that commits itself to compliance with the UPR. In response to these gaps, we propose a structural account of constitutional justice that is both Kantian-congruent and consistent with the basic facts of contemporary, rights-based constitutionalism. We thus confront the following question: what components of a system of constitutional justice would optimise a community’s capacity to achieve Public Right?

The first step is to conceptualise constitutional rights as positive requirements of legality. Rights – substantive limitations on the exercise of public authority, along with standing and due process requirements – are justiciable commands. Every official owes a duty to make and enforce laws in a manner consistent with the UPR, and to refrain from subjecting individuals under their authority to coercive rules that are inconsistent with the UPR. And every individual has a right to defend their rights in a lawsuit.

Conceived in Kantian terms, rights formally express external freedom in law for individuals, however imperfectly realised or under construction. Rightful Honour restricts the consent of the People in ways that limit rights provisions. Kant, himself, derived the content of a few rights from Rightful Honour, including freedom of expression, religious liberty,^{Footnote 6} and the presumption of innocence (MM 6: 238). An expansive notion of freedom of expression, for example, is linked to the right to be one’s ‘own master’ (MM 6: 238). Limiting expression is appropriate to prevent one person from depriving another of her own capacity as a free and honourable agent; thus, one may not impugn another’s reputation, or deprive them of choice and Rightful means through fraudulent inducement (Ripstein Reference Ripstein2009: 210). The right to the presumption of innocence is also rooted in the foundational principles: to be treated, presumptively, as ‘a human being beyond reproach’ (MM 6: 238). And Kant bluntly states that ‘no human being in a state can be without any dignity’, before explaining why slavery must be categorically forbidden (MM 6: 330).

The principles of Innate Freedom and Rightful Honour imply that certain rights, such as freedom from being enslaved, are absolute, insofar as no legitimate, UPR-compliant reasons can be given for their infringement. Absolute rights are those that are required to secure a person’s place as a juridical person in a system of equal freedom writ large. Most rights in modern constitutions, however, are not expressed in absolute terms, but are ‘qualified’ by limitation clauses. Qualified rights command the omnilateral lawmaker to secure the reciprocal freedom of all in law. In Kantian terms, such rights recognise the individual’s entitlements to set and pursue ends, while providing reasons for officials to restrict the scope of those same entitlements, in order to realise Public Right.

The distinction between absolute and qualified rights is not always obvious. Consider the right to life and the prohibition of slavery.^{Footnote 7} The latter is an absolute right, because it amounts to a complete deprivation of a person’s entitlement to freedom. There are no UPR-compliant reasons which could justify imposing this status – a denial of juridical personhood – on anyone. By contrast, the right to life has an absolute dimension, in that it safeguards a person’s purposiveness as such. But there may well be UPR-compliant reasons licensing the state to take someone’s life. The state might kill person X, for example, in order to prevent X from depriving Y of life. The maintenance of a system of equal outer freedom may, at times, depend on the use of lethal force when there is no alternative means of protecting the freedom of others or all. Under this view, only the core of the right to life – a right against being arbitrarily put to death, or killed for the sake of private ends – is absolute.

We can push Kant’s method of deriving entitlements further, to sketch a picture of a charter of rights as foundational norms of justice in law. Again, the key is to consider the UPR as a legal obligation binding on the exercise of state authority. Thus, the constitutional contract places officials under a duty, owed to every person subject to their authority, not to make or enforce law in ways that are inconsistent with their rights. When it comes to qualified rights, the legitimacy of the justification for the limitation of one’s freedom will turn on its consistency with the UPR. Further along, we will propose a way of conceptualising the proportionality framework as an analytical procedure for arriving at answers to precisely this type of question. Before doing so, we need to bring judicial review into the picture.

VI. The constitutional court as omnilateral trustee

We have argued that an enumerated bill of rights deserves pride of place in a Kantian constitutional order. The rights-based constitution converts the idea of the original contract into positive constitutional law, while delegating to officials the authority to secure Public Right. Kant insisted that it was the cardinal duty of every official to give effect to the normative principles extrapolated and defended in the Doctrine of Right, without which a just, constitutional order could never be realised. Enforcing the charter of rights would, in effect, operationalise the UPR as the basic criterion of law’s legitimacy. In this constitutional order, some rights will be expressed in absolute terms, but most will be qualified by limitation clauses that expressly authorise lawmakers to infringe on freedoms when necessary to achieve Public Right.

We now take on the task of describing a Kantian-congruent system of constitutional judicial review, a topic on which he wrote virtually nothing. Our claim is that Kantian theory requires a ‘constitutional court,’ which we define as an apex, omnilateral organ of governance whose mission is to supervise compliance with the UPR. The Court (i) evaluates the rights-regarding acts of all other public officials, (ii) issues authoritative interpretations of the content, scope, and application of the charter, (iii) certifies that officials act according to the UPR, and (d) invalidate acts that violate rights.

Delegation theory is directly relevant to this situation.^{Footnote 8} Kant elaborates an abstract, functionalist claim to the effect that the move to omnilateral governance must take place if the polity is to progress toward a Rightful civil condition. The written constitution, a formalised act of delegation by the sovereign People, authorises public officials to make and enforce law in order to realise a Rightful civil condition. In pursuing this same tack, one confronts an obvious agency problem: how do the People ensure that officials will act according to the UPR? At the very least, allowing leglislators to sit in judgement of their own statutes would make it impossible for citizens to distinguish a proper public act from one that pursues a private or an illicit interest.^{Footnote 9} Citizens would also not know if an act violates the UPR. The constitutional court is the institutional solution to this problem.

Yet the problem that generates the demand for a constitutional court runs deeper still. Correlative to the state’s duty to govern in a manner consistent with the UPR is the Innate Right of each person to freedom. Rights-as-freedom will be illusory unless each person subject to the state’s authority is entitled to challenge state action. For Kant, a right is a moral power held by each citizen, a juridical title to act or be in a condition. If he is correct, then citizens can invoke a right in order to justify their acts or positions. But qualified rights are more than that: they authorize state officials to coerce.^{Footnote 10} It follows that for Innate Freedom, and its positive determinations in explicit constitutional guarantees, individuals must have a legal power to constrain wrongdoing on the part of state officials. A right against the state requires as much.

This creates a prima facie difficulty for constitutional rights. The power to coerce state officials into compliance with the UPR cannot be operationalised through private acts of resistance, on pain of rendering the omnilateral will of the state subject to the unilateral say-so of each person. Put differently, if Innate Freedom transmutes into a sequence of justiciable positive rights held by each person, then each person also possesses a title to constrain officials from wrongfully interference with their freedom.^{Footnote 11} Once activated, the constitutional court determines the scope and application of a pleaded right; but its ruling will not be based on the unilateral judgment of the claimant, but on the constitution itself, the foundational act of the will of the People.

No other institution could perform this crucial, adjudicative function. In a system of parliamentary sovereignty, notwithstanding the commitment of the legislature to respecting rights (an empirical not a juridical state of affairs), individuals possess no entitlement to demand legislative compliance with the UPR. Rather, such a system recognises only a collective power to hold the legislature accountable, through voting and public deliberation (Weinrib Reference Weinrib2014). Where no one possesses an individualised title to require the state to comply with the terms of the UPR, no one holds a genuine right, and the legitimacy of the law can not be assured.

Consider the ‘new commonwealth model’ of constitutionalism (Gardbaum Reference Gardbaum2012), which purports to reconcile legislative supremacy with rights protection. That model features (i) a charter of rights, (ii) some form of judicial power to review legislation and other government acts for consistency with the charter, trumped by (iii) a legislative ‘final word’ that will determine whether law judged to be inconsistent with a right provision will nonetheless remain in force. While the model gives standing to individuals to challenge wrongful state action, the legislature can choose to maintain a statute that violates rights. This is a version of what Kant called despotism: ‘the autonomous execution by the state of the laws which it has itself decreed’. In such a situation, ‘the public will’ expressed in the constitution is ‘administered by the ruler at his own will’ (PP 8: 352). A majority within the legislature, rather than pre-existing constitutional rules, determines the resolution of the conflict.

As a practical matter, the capacity of the constitutional court to render justice will depend upon an extensive grant of power and jurisdiction. The authority to review the conformity of statutes with rights and the UPR is required. Prohibited are arrangements that (i) restrict the binding authority of legal statements in judicial opinions to the parties of the judgment, or (ii) ascribe to the legislature the competence to make determinations regarding the scope and content of rights, but withhold them from the judge, or (iii) require judges to defer to non-judicial officials in rendering such determinations. Rights must be justiciable with respect to all public acts. In a system designed to achieve Public Right, the Court will oversee, and therefore participate in, omnilateral law-making. But its primary role is to adjudicate constitutional disputes that arise from the omnilateral law-making of officials. Put in the language of delegation theory, although the Court is an ‘agent’ of the People, the situation is one of trusteeship (Thatcher and Stone Sweet 2002: 7).

In sketching a simple model of trusteeship, we can express more formally the role to be played by the constitutional court.^{Footnote 12} Through legislating a rights-based constitution, the People have placed the ultimate value – their freedom – in trust. The constitution confers judicial review powers on the court, for the purpose of enforcing rights as positive requirements of legality. It places officials under the constitutional obligation to act according to the UPR, as a means of constructing Public Right; and it tasks the constitutional court with monitoring their compliance with this obligation. The court can only properly perform its mission if it possesses the authority to invalidate any public act that violates a right provision, and its decisions are effectively insulated from override on the part of the public officials whose decisions it controls.^{Footnote 13}

We recognise that this part of our argument – that Kantian imperatives generate a powerful functional demand for the structural supremacy of a ‘trustee court’ – will be controversial. The claim, however, does not conflict with Kant’s own pronouncements, spare as they are, on legislative power and justice. As noted, Kant defined the state as a ‘union of a multitude of human beings under laws of Right’, and asserted that ‘it is only in conformity with the conditions of freedom and equality that [the] people can become a state and enter into a civil constitution’ (MM 6: 313, 315). Under this constitution, the people govern themselves collectively:

Today, we no longer have to understand the idea of an ‘original contract’ as a purely regulative ideal; the People typically manifest themselves when they enact new constitutions, say, through a referendum. The rights-based constitution delegates law-making authority to various organs and officials, while the charter of rights constrains the exercise of that authority. Given a conflict between a rights provision and any legislative act, the former prevails.

In such a situation, neither parliamentarians nor executives are principals in relation to the constitutional court; instead, they are agents of the People, and the People have commanded the court to supervise the decision-making of all officials. Kant himself equated judicial authority with justice:

Today, when it comes to rights-based constitutionalism, the People, as primary lawmakers, have legislated judicial supremacy. Parliamentarians are secondary lawmakers, agents of the People, and subject to the decisions of the trustee court. Constitutional judges are caretakers, stewards, of the regime.

It should be obvious that a system that features the supremacy of an authoritative constitutional court fatally undermines the usual presumptions of delegation theory, which are exemplified by the simpler Principal–Agent models of the social scientist. In ‘agency-control’ models, a unified Principle possesses the means to control the acts of her Agent on a continuous basis. A trustee, however, is a special type of agent. In this instance, the court is entrusted with promoting the values placed in reserve by the People: their freedom. The People, as the constituent legislative power, are also the beneficiaries of the trust going forward. The constituent power alone possesses the authority to alter the terms of the trust, which it may do through revising the constitution (Stone Sweet (2012b: 820–5).

Trust law offers further analogies that are appropriate to our argument, notably, in its emphasis on fiduciary duties. Because both citizens and officials are vulnerable to the Trustee court’s judgments, the judges are bound by a set of robust obligations. The most important of these fiduciary duties – typically formalised as (i) loyalty, (ii) accountability, and (iii) deliberative engagement – apply to the trustee judge (Leib, Ponet and Serota Reference Leib, Ponet and Serota2013; Stone Sweet and Brunell Reference Stone Sweet and Brunell2013). As Leib et al. (2013) argue, loyalty refers to the judge’s duty to protect rights in ways that ensure that public officials act in accordance with the UPR. The duty of accountability requires the Court to justify its rulings with reasons. And the obligation of deliberative engagement requires the judge ‘to engage in dialogue’ with those who are vulnerable to her rulings, which includes both rights claimants and officials. The latter entails ‘an authentic effort to uncover preferences rather than a mere hypothetical projection of what beneficiaries might want’ (Leib, Ponet and Serota Reference Leib, Ponet and Serota2013: 699).

In Kantian terms, a robust fiduciary construction of trusteeship will underwrite reasons individuals have to accept state coercion. As a matter of positive law, each person retains the right to challenge any decision that would infringe upon their rights, and every official is placed under a duty to justify acts under review in terms that are comprehensible under the Doctrine of Public Right. In our view, the right to justification ^{Footnote 14} cannot be optional. Instead, it comprises a meta-rule that commits the polity to procedures that are conducive to the construction of Public Right. Arguably, in Perpetual Peace, Kant implied such a right in short but important remarks on ‘publicity’:

Kant goes on to pronounce a ‘transcendental formula of Public Right’, according to which ‘all actions that affect the rights of other human beings which are incompatible with publicity are unjust’ (PP 8: 381). Scholars differ on how best to interpret Kant’s insistence on the principle of publicity (Davis Reference Davis1991; Laursen 1986). For present purposes, we understand it as presumptive support for a right to justification (held by all citizens) and its corollary, a reason-giving requirement (binding on officials). More generally, a reason-giving requirement is a functional necessity for any system of constitutional justice, if it is to develop effectiveness (Stone Sweet (2012b). In any event, the right to justification must be reflected in rules of adjudication, including standing (access to justice), the fiduciary duties of the Trustee court (accountability and deliberative engagement), and in constraints on the exercise of public authority by officials (reason-giving, as disciplined by the UPR).

In this same spirit, we now address the question of why the trustee court ought to embrace the proportionality principle, or some (currently unknown) principle that performs better than proportionality, if it is to fulfil its mission.

VII. The new constitutionalism and the proportionality principle

Since 1950, the gradual consolidation of rights-based constitutionalism has transformed the global political and legal landscape. The precepts of this ‘new constitutionalism’ can be simply stated:

1. (i) state organs are established by, and derive their authority from, a written constitution;

2. (ii) the constitution assigns ultimate power to the People by way of elections or referenda;

3. (iii) the exercise of public authority, including legislative, is lawful only insofar as it conforms with the constitutional law;

4. (iv) the constitution provides for a catalogue of rights and a mode of judicial review to defend those rights; and

5. (v) the constitution is entrenched, specifying how it may be revised.

As an empirical matter, virtually every new constitution adopted over the past three decades established systems of justice in line with this template.^{Footnote 15} These developments make Kant’s theory of Public Right directly relevant to constitutional practice.

One can treat our model of Kantian justice as an ideal type for heuristic comparative purposes. The model bears more than a surface resemblance to the most important domestic systems of justice operating in the world today; in these, certain norms and stipulations are treated as necessary determinants of more specific rights, and of constitutional legality itself. Well-known examples include the case of the right to dignity in the German Basic Law,^{Footnote 16} the requirements of ‘equal citizenship’ in ‘a free and democratic society’ found in the Canadian Charter of Rights and Freedoms,^{Footnote 17} or the values of ‘human dignity, equality, and freedom’ that are synthesised in Constitution of the Republic of South Africa.^{Footnote 18} These formulations come before the listing of more specific rights and, in most contemporary constitutions,^{Footnote 19} the catalogue of rights comes before the constitution of state organs. In post-World War II constitutions,^{Footnote 20} almost all rights are qualified by limitation clauses, yet another Kantian gloss. Omnilateral, law-making organs operate under a continuous obligation to generate a determinate legal ordering that conforms to rights; and a trustee court resolves legal disputes within that ordering.

Under the Doctrine of Public Right, law’s legitimacy is subjected to the dictates of a covering principle – the UPR – which, in turn, is rooted in the principles of Innate Freedom and Rightful Honour. Indeterminacy is built into both rights provisions and the UPR. The fraught question – ‘under what circumstances does an absolute right apply?’– bedevils even the most refined systems of constitutional justice. Qualified rights are indeterminate, incomplete norms by definition and design. Whether officials have abused powers delegated to them by a derogation clause is a question that cannot be settled by referring to, or conceptualising dogmatically, the right, or the public interest that lawmakers pursue. Further, because the limitation clause incorporates the public interest into the right, the usual conflict rules are useless. One cannot appeal to hierarchy or the primacy of the right or the public interest in the abstract, since both parties are, in fact, pleading the same norm. Applying the lex posterior derogat legi priori rule is also prohibited, since the adoption of any new statute would automatically eviscerate the rights claim, the basis of which dates from the adoption of the constitution. In a situation in which a rights claim comes into conflict with a legitimate public interest, the best constitutional judges can do is to embrace proportionality analysis [PA].

In fact, over the past 50 years, the world’s most powerful constitutional courts have institutionalised PA as the dominant, ‘best-practice’ doctrinal framework for adjudicating qualified rights (Stone Sweet and Mathews 2008; Mathews and Stone Sweet 2011; Kumm Reference Kumm2004; Reference Kumm2010; Barak Reference Barak2012a). PA belongs at the very centre of a Kantian system of constitutional justice, for three interrelated reasons. First, it permits judges to give broad scope to any qualified right being pleaded, mirroring Kant’s argument that all positive rights held against public officials give concrete expression to a single unitary right to Innate Freedom, rather than a succession of discrete rights whose scope might, in principle, be quite limited. Most contemporary rights-based constitutions proclaim a general right to liberty, to which the qualified rights give specific content. The trustee court, in accepting the validity of a claim based on a qualified right, does not thereby resolve the case but, rather, requires the official to justify the act that has burdened the claimant.^{Footnote 21} Second, PA commits judges to the systematic evaluation of such justifications. Under PA the crucial question is always, as Kumm (2010: 42) puts it, ‘whether a public action can be demonstratively justified by reasons that are appropriate in a liberal democracy’, given the paramount importance of rights in modern constitutionalism. Third, a trustee court that deploys PA consistently and in good faith will fulfil the fiduciary duties discussed above (Stone Sweet and Thomas Brunell (2013: 69), of loyalty (to constitutional values), accountability (through reason-giving), and deliberative engagement (with rights-holders and officials). PA thus gives procedural structure to the right to justification, strongly implied by Kant himself (discussed above), ‘in terms of public reason’ (Kumm Reference Kumm2010: 144, 150).

We now provide a brief summary of PA, and sketch how a Kantian trustee court would presumptively deploy it.

VIII. Proportionality and qualified rights

PA is tailor-made for resolving disputes that involve a conflict between a rights claim and a public act whose constitutional legality, officials alleged, is covered by a limitation clause. In the latter, paradigmatic, situation, the analysis proceeds step by step, as follows.

In a preliminary phase, the judge considers whether a prima facie case has been made to the effect that a government act burdens the exercise of a right. By convention, the judge will use this occasion to discuss the jurisprudential theories that underpin the pleaded right, as well as prior rulings and other legal materials that will bear upon the court’s determination of the right’s scope and application in the case at hand. In its most developed form, PA then proceeds through a sequence of four tests: (i) ‘legitimacy,’ or ‘proper purpose’; (ii) ‘suitability’; (iii) ‘necessity’; and (iv) balancing in the strict sense. A government measure that fails any one of these tests violates the proportionality principle and is therefore unconstitutional.

The first stage of PA mandates inquiry into the ‘legitimacy’ of the measure under review: the judge confirms that the constitution authorises the government to take such a measure, typically, under a limitation clause (express or implied). In most jurisdictions, judges effectively treat the proper purpose prong of PA in the style of a threshold inquiry: if the constitution has not authorised the state to pursue such a purpose, then the rights claimant must prevail. In the second step – ‘suitability’ – the government must show that a rational relationship exists between the means chosen and the ends pursued, such that the former is ‘suitable’ to achieving the end (which, the first test has already confirmed, constitutes a legitimate public purpose). In most systems, few laws are struck down on grounds that the official purpose is illicit (per se illegitmate), or that the act is irrational or arbitrary (the means being unsuitable).^{Footnote 22}

The third phase – ‘necessity’ – has far more bite than the suitability inquiry. At its core is a least-restrictive-means (LRM) test,^{Footnote 23} through which the judge ensures that the measure under review does not curtail the right being pleaded more than is necessary for the government to achieve its declared purpose. In practice, judges do not invalidate a measure simply because they can imagine one less restrictive alternative. Instead, most PA-adept courts insist that policymakers have a duty to consider a range of reasonably available alternatives, and to refrain from selecting the most restrictive among them. These courts also typically require, as a pleading matter, that the rights claimant identify less restrictive alternatives; and the judges will never strike down a law as unnecessary without comparing it to at least one reasonably available alternative.

An act that fails either the legitimacy or suitability tests is one that contributes nothing to the realisation of Public Right. Ends must meet the dictates of the UPR, and any limitation of a right through means that are not rationally connected to a legitimate end must constitute a per se infringement of freedom. These same considerations suggest that the use of means other than those that are least restrictive on freedom must also qualify as a violation of the UPR: no official possesses the authority to restrict freedom further than is necessary to secure the external freedom of all. Thus, irrespective of the importance of the end being pursued, a public act that fails a LRM test is one that can not be justified under a system of Public Right.

In the proportionality world, the analysis cannot end with necessity. If it did, a law that imposed an unjustifiable burden on the rights holder, but was nonetheless narrowly tailored, would prevail. A fourth stage, balancing in the strict sense, is required. In it, the court assesses, in light of the facts or policy context, the act’s marginal addition to the realisation of Public Right against the marginal injury incurred by infringement of the right. Thus, one core function of balancing is to ensure that a relatively small or even trivial addition to the public weal does not, say, curtail a right in a significant way. Judges that rely heavily on this stage (e.g., members of the GFCC and the Israeli Supreme Court), also emphasise that balancing allows them to ‘complete’ the analysis, in order to check that no factor of significance to either side has been overlooked in previous stages (Grimm Reference Grimm2007: 393–5; Mathews and Sweet Stone Reference Stone2011: 106–8).

Consider the US Supreme Court’s ruling in United States v O’Brien (1968).^{Footnote 24} Mr O’Brien had burned his draft card, in violation of federal statutes, while protesting the Vietnam War and military conscription. The Court took no firm position on the question of whether O’Brien’s ‘wordless’ act was protected by the First Amendment; the answer to that question was left incomplete in comparison to what is required under PA. Instead, the Court formulated the following test:

On the basis of this test, the Court upheld O’Brien’s conviction, since the draft card fulfilled various administrative functions. The judgment, however, concluded in deafening silence on the question of the relative importance of government’s interest and O’Brien’s ‘alleged’ speech right. Under PA, the judge would have been required to give an answer to that question, in the balancing stage. The Court, however, marched through the test just announced – which embodies the first three stages of PA – while saying virtually nothing about the First Amendment. It is worth emphasising that O’Brien still may have lost the case under a full-fledged version of PA. But an additional layer of reasons would have been added, thereby completing the analysis.^{Footnote 25}

It makes little sense to discuss the balancing stage without invoking, from the outset, the formulations of Robert Alexy (Reference Alexy2002) and Aharon Barak (Reference Barak2010, Reference Barak, Rosenberg and Sajó2012b). Alexy (2002: Postscript, 390–425), synthesising the jurisprudence of the GFCC, proposed the Law of Balancing:

For his part, Barak (2012b: 746) elaborates the Rule of Balancing:

Barak (2010: 10) insists that the balancer must take account of the significance of the right in context:

Both formulations stress the duty of the judge to engage in relational analysis of the values in tension, in the context of a specific dispute. And both will drive the judge toward an answer to the dispositive question: does the law under review burden liberties too much, given our constitutional commitment to rights?

A Kantian reading would convert these formulations into strictures for ensuring that the law can be justified under the UPR.^{Footnote 26} As Barak (2012b: 745) suggests, ‘balancing’ is only a metaphor for what judges do at this stage:

Balancing in the strict sense bears no relation to cost–benefit analysis in a crude utilitarian sense which, in our view, would be anathema to a Kantian approach. Proportionality balancing involves assessing the relationship between the most important requirements of the constitutional order, both of which are Kantian values: (i) the freedom of every individual, embodied in the individual right at issue, and (ii) the duty of state officials to achieve Public Right, to be (partially) effectuated through the realisation of the governmental purpose at stake. In the Kantian model, these requirements are not strictly incommensurate: both are subsumed by the UPR, that is, by the concept of freedom within a Rightful civil condition. Balancing comprises a holistic evaluation of whether, given the circumstances and our constitutional commitments, officials are justified in taking a measure, given their duty to create a system of reciprocal constraints on freedom.

The ‘balancing’ inquiry attends to the propriety of a particular means of advancing public interests – of constituting Right – not a consequentialist operation of weighing interests against one another. Rather than relying on a metric of evaluation exogenous to the system of Right, or attributing atomistic weights to principles, the Kantian account we have developed considers all dimensions of importance within a single universal system of freedom. A law that is judged to be proportional comports with the UPR, and can thus be credited as a contribution to Public Right. A law that is disproportionate makes no such contribution, and is therefore invalid.

Kant insisted that a system of Public Right could only be produced through a sustained process of practical reasoning, to render the determinable more determinate, not to discover answers to questions that are beyond the realm of reasonable disagreement (PP 8: 366–7, 386; and MM 6: 230–1, 317–20, 340–9, 354–5). In Barak’s formulation, the judge’s task is to determine whether a law falls within a zone of proportionality; in Kantian terms, the question is whether the law can be justified under the UPR, which is coterminous with that zone. The outcome will depend on an assessment of the severity of the infringement in context, whether the activity or condition covered by the right falls within the right’s core or periphery, and the availability of alternative measures, all of which demand sensitivity to empirical circumstances, as they change over time (Barak (Reference Barak, Rosenberg and Sajó2012b). We find Barak’s exposition of balancing Kantian-congruent. Its function is to adjust the aspects of the constitutional order in relation to one another, on an ongoing basis, so that they fit together into a coherent whole.

PA has many critics. Some see potential dangers: judges may use PA as a cover for deferring to legislators and executives, or for balancing rights away. Others see PA as being too restrictive of policy discretion, inevitably casting judges as masters of the policy processes under review. Proponents defend proportionality against attacks from both sides (Stone Sweet and Mathews 2008; Mathews and Stone Sweet 2011). It is important to emphasise that PA is an analytical procedure. PA does not, in itself, produce substantive outcomes; and it does not tell judges how important are any two contending values and interests. Instead, PA organises the systematic review of justifications for government measures that would burden the exercise of a right. Judges also use PA to build secondary doctrine: the argumentation and justification frameworks that will govern adjudication (and hence policymaking) in any domain covered by a specific right. As we argued in the last section, a meta-rule – melding the entitlement to justification and the reason-giving requirement – is a necessary component of any effective system of constitutional justice. Adopting PA places this meta-rule at the very heart of adjudicating rights, and the enforcement of the UPR.

IX. Excluded reasons and absolute rights

PA neatly fits the demands of the UPR and structures how judges will fulfil their fiduciary obligations. Yet, with regard to the first stage of the framework – legitimate purpose – Kant’s ideas arguably point away from necessity analysis and balancing, and towards a mode of decision-making in which the judge’s principal task is to exclude illegitimate justifications for limiting freedom, thereby determining the scope of the right.

As noted, when adjudicating qualified rights, most skilled judges treat the legitimacy prong of PA in the style of a threshold inquiry: if the constitution has not authorised the state to pursue such a purpose, then the claimant must prevail on the basis of little more than a prima facie demonstration that a right is in play. Except in the most egregious cases, the law under review will pass this prong of PA without much ado. After all, the competence to regulate is conferred on officials by the rights provision itself, through a limitation clause. Without further contextual clarification, the outcome conforms to Kantian dictates: officials may hinder the freedom of any rights holder, but only to secure the external freedom of all. If a system contains a general right to liberty, then officials may act only to secure the external freedom of all.^{Footnote 27} Further, officials may also routinely claim that the act under review had been designed to fulfil a right, thrusting the court into a balancing posture. In the proportionality world, judges and scholars typically downplay the importance of proper purpose inquiry, deploying it most often to pay their respects to officials’ good faith efforts in pursuit of valid public interests, saving any censure for later stages.

This de facto insouciance deserves more scrutiny. Simplifying a complex issue, a more robust, sustained inquiry into legitimate purpose could well subsume the types of reasoning found in subsequent stages. Concrete constitutional guarantees can only be limited for the sake of freedom; and ends that are exogenous to the system of Right are impermissible bases for restricting freedom. Because the Kantian judge is under a clear duty to filter out such ends, one should ask why the legitimate purpose test is not sufficient in itself, that is, why supplement it with three subsequent stages?

If judges focused more attention on proper purpose, treating the legitimacy prong as a general test of legality, then it would likely evolve as the privileged site for the elaboration of categorical, means-based restrictions. As it is, suitability and necessity analysis (both which help courts ‘smoke out’ illicit motives), and balancing (through which courts assess the proportionality of marginal benefits and harms) do the work that, arguably, could be done in proper purpose analysis. In the proportionality world, one typically asks (i) whether a purpose is constitutionally legitimate in the sense that the aim pursued can be subsumed under a legal power that state officials rightfully possess. But one could also wonder (ii) if a purpose is constitutionally legitimate only once the judge finds that the end is itself a sufficient reason for restricting a right in the first place. The latter situation requires categorical reasoning, not just pro forma box ticking.

To bring the point into focus, consider the well-known trolley problem, which involves two scenarios (Jarvis Thomson 1985). In the first, a runaway trolley will kill five people unless a bystander switches the trolley onto another track where, foreseeably, it will kill only one person. In the second, a runaway trolley will kill five people, unless a bystander pushes an enormous man in front of it, as a means of triggering the emergency break. The standard intuition associated with this pair of cases is that diverting the trolley is permissible, but pushing the man in front of the trolley is impermissible (Cushman, Young and Hauser Reference Cushman, Young and Hauser2006).

A robust legitimate purpose test would ask whether saving the lives of the five could constitute a legitimate reason for violating the right of the man against being used as a means. On the Kantian view, the answer to this question is clearly ‘no’: each person possesses an entitlement to be one’s own master, and not to be used for another’s ends. This secures the man’s right against being conscripted into the purposes of the five, no matter how urgent their situation. The crucial point is that the analysis proceeds by way of categorical reasoning, not through assigning weights to benefits and harms, and then balancing.

One powerful defence of PA, however, rests on the distinction between absolute and qualified rights.^{Footnote 28} Once the constitution or judge classifies a right in absolute terms, it is removed from the domain of proportionality. Famously, the GFCC refuses to apply PA to dignity, on grounds that are strikingly Kantian. In the Life Imprisonment Case (1977), adjudicating whether life imprisonment is lawful under the banners of retribution and deterrence, the Court held that:

The GFCC sidesteps the issue raised here – whether the policy reflects an improper purpose – by categorising the dispute as directly involving the individual’s dignity, which prohibits PA altogether. In another full-fledged dignity ruling, Aviation Security (2006), the GFCC invalidated, on dignity grounds, a statute that would have authorised the interior minister to shoot down an airliner that had been hijacked by terrorists with the intention of using it as a weapon against the population.^{Footnote 30} The Court’s rationale is overtly neo-Kantian: to allow an official to intentionally terminate the lives of the innocent persons on board would convert those persons into objects of the state.^{Footnote 31} In cases in which dignity is directly and fully implicated, the Court applies PA.

The issue of whether courts should develop a more robust application of the legitimate purpose test deserves more consideration. In the proportionality world, however, no court has moved in this direction in any consistent way. Such a move might very well lead to the migration of balancing considerations into deliberations on proper purpose, a type of ‘hydraulic effect’.^{Footnote 32} While the US Supreme Court sometimes adopts a categorical posture, for example, it often engages in balancing to produce the categorical rule (Aleinikoff Reference Aleinikoff1987; and Mathews and Stone Sweet 2011). Put in terms of PA, balancing and necessity reasoning would likely flow into the analysis of proper purpose. Such an outcome would undermine transparency, as well as the tribunal’s capacity to express respect for officials precisely where it is due.

X. Proportionality and judicial supremacy

The mission of the Kantian trustee is to supervise the rights-regarding acts of all other officials, to assess reasons officials give when they burden any right, and to invalidate laws when these reasons are insufficient. Insulating the court’s rulings from override – by those over whom the court exercises authority – will be an important determinant of the system’s effectiveness (Stone Sweet 2012b).

Judicial supremacy raises well-worn legitimacy concerns, including the so-called ‘counter-majoritarian difficulty’: the capacity of the trustee to generate policy outcomes that elected officials would not have produced on their own, but which are difficult or impossible to reverse. Under such conditions, the override or revision of important rulings on constitutional rights is, in practice, only possible through subsequent rounds of adjudication. The court that adopts PA – a highly intrusive standard of review – makes its formal supremacy a mundane fact. Indeed, the necessity and balancing prongs position a trustee court to be the supreme lawgiver, albeit through the adjudication of disputes that arise within parameters set by prior acts of law-making and the constitution.

While we recognise that supremacy raises deep normative issues, Kantian theory is largely immune to counter-majoritarian objections.^{Footnote 33} Kant gives freedom – rights – pride of place, not the will of a transient, political majority. For Kant, representation and accountability demands more than occasional consultation of the People as an electoral body. It requires accountability to the People considered as individual citizens, whose entitlements to rights are unimpeachable, and to the People as constitutional legislators. To the extent that the People have legislated supremacy, placing the parliament under the control of a constitutional court, normative arguments grounded in the dogmas of legislative sovereignty are beside the point. We have not argued that courts are the repository of some type of special wisdom when it comes to enforcing rights. We do claim that trusteeship – supremacy constrained by robust fiduciary obligations – will optimise the polity’s capacity to progress in its goal of achieving a Rightful constitutional condition.

As an empirical matter, modern systems of constitutional justice are, in fact, characterised by judicial supremacy (Stone Sweet 2012b). How effective systems of constitutional justice actually operate should bear on the normative debate. Three points, each of which is based on strong empirical findings, deserve strong emphasis. First, the most effective constitutional courts are those able to draw other policymakers, and at times the citizenry, into the discourse they constitute and curate as a jurisprudence of rights (Stone Sweet 2000). If officials and citizens ignore, or conspire to undermine the consequences of, its rulings, then trustee courts will fail. Second, the ongoing use of PA creates an interface for deliberative engagement between the constitutional court and all other officials who make and enforce law (Stone Sweet and Mathews 2008: 104–60). Successful trustee courts use PA not to bludgeon officials into submission, but to construct (often intricate) ‘dialogues’ with legislatures, executives, and the ordinary courts concerning the scope of their own law-making authority. These same courts have strongly embraced PA, an operating system for dialogue, which shapes the evolution of policy and the content of the rights-based constitution (Stone Sweet 2000; Hiebert Reference Hiebert, Campbell, Ewing and Tomkins2011). Third, legislatures and executives are unlikely to render a charter of rights effective on their own, without having their decision-making placed in the shadow of a trustee court. This last point firmly applies to the new commonwealth model.^{Footnote 34}

XI. The multi-level architecture of right

Right, Public Right, International Right, and Cosmopolitan Right share certain micro-foundations in common, and each purports to resolve the same generic problem. Flikschuh puts the point neatly:

The implication for any Kantian system of constitutional justice should be clear: for all ‘human relations’ (Williams Reference Williams, Follesdal and Maliks2015), at every level of governance, the UPR constitutes a foundational criterion of the legitimacy of all law.

The UPR lies at the core of any Rightful constitutional condition for two reasons. First, it complies with, and flows outward from, even more primordial principles: Innate Freedom and the Internal Duty of Rightful Honour. Second, Kant casts the UPR as a meta-norm: all officials are under a duty to make, interpret and apply law in conformity with the UPR; and any act that conforms to it commands obedience. In Kelsenian terms, the UPR gives to the Grundnorm substantive content, in the form of a command. In Hartian terms, the duties that inhere in the UPR take primacy over all other secondary rules (Hart Reference Hart1994: 92–4).

Extending our account to a transnational system of rights protection is, therefore, relatively straightforward. To illustrate, consider the European Convention on Human Rights. The states signatories placed the supreme constitutional value – freedom – in trust, in the form of a charter of human rights. As agents of (and analogous to) the People at the domestic level, they have assumed the role of the constitutional legislator. With Protocol No. 11 (1998), the Contracting States created a version of trusteeship. The European Court protects the rights of individuals within and beyond the state: a ‘justice’ function. It supervises the rights-regarding activities of all national officials: a ‘monitoring’ function. And it authoritatively determines the content and scope of convention rights on an ongoing basis: an ‘oracular’ function (Stone Sweet 2012a).

Kant does not, however, apply the ‘idea of the original contract’ with respect to inter-state relations. Instead, he asserts that states (i) are under a moral duty to pursue the construction of a Rightful condition, and (ii) will be more likely to succeed if in league with one another. In Perpetual Peace (8: 354–8), Kant counselled member states of leagues to retain their sovereignty, at least during the foundational period. The regime’s organs should not exercise direct, juridical authority within the states that make up the federation. Among other primary tasks, the Strasbourg Court enforces the absolute prohibitions contained in Articles 2 and 3 ECHR; and it adjudicates the qualified rights of Articles 7–11 ECHR according to the proportionality principle, while requiring all domestic courts in the regime to use PA. It is the authoritative interpreter of the Convention, and its rulings are strongly insulated from reversal. But the Court does not possess the power to invalidate national law that conflicts with Convention rights, a competence that falls within the realm of domestic justice. As argued in A Cosmopolitan Legal Order, a multi-level system of justice was constituted in Europe through the combined effects of (i) Protocol No. 11, which conferred on all individuals the right to petition the European Court after exhaustion of national remedies, and (ii) the incorporation of the Convention in ways that enable the courts to enforce it directly, as national law (Stone Sweet (2012a). As a result, the interface between domestic and transnational systems of justice has become increasingly articulated. At the same time, it is obvious that the European Court’s effectiveness depends critically on the performance of domestic trustee courts.

Kant himself (PP 8: 356) pointed to the dynamic relationships – interactive, ‘feedback’ effects – of the different levels of Right. These effects could ‘undermine’ progress toward a Rightful condition, and might even lead the process to ‘collapse’. But they could also reinforce it. Once formerly despotic states become republican, others may choose to follow, as the benefits of doing so become apparent. And a Rightful condition beyond the state can help support the consolidation of Public Right at the domestic level. Indeed, Kant imagines the establishment of ‘a republicanism of all states, together and separately’ (MM 6: 354–5) under a shared doctrine of Public Right. In any event, the pathways through which perpetual peace and a Rightful condition can be achieved are likely to be complex, non-linear, and fraught with political obstacles. ‘As Kant was often to note’, Williams (Reference Williams, Follesdal and Maliks2015) reminds us, ‘the human race does not progress the easy way. It only adopts rational principles for governing its social relations after a hard and frequently violent struggle with itself and its worst characteristics.’

Kantian constitutional theory is, therefore, powerfully integrative, requiring us to consider, simultaneously, the cosmopolitan nature of constitutional rights, and the constitutional grounds of the cosmopolitan (Brown Reference Brown2009; Kumm Reference Kumm2016).