Facebook’s right to monitor its platform conflicts with a user’s right to post political opinions. A baker’s right to religious liberty runs up against a same-sex couple’s right to equal service. A private school administration’s right to set health policies on its campus collides with a person’s right not to wear a mask. Rights are invoked across a wide range of political disputes by a diverse set of actors – large corporations, small proprietors, and individual people, to name a few. These are all private parties, not state actors, and in a traditional model of constitutional rights, none could claim a constitutional right against the other. The constitution applies only to government action, whereas relationships among private companies or individuals fall under separate areas of law, often defined by ordinary legislative processes relating to antitrust, antidiscrimination, or public health initiatives, for example. The constitution simply is not at issue in these cases.

This traditional understanding of constitutionalism is often understood as a vertical model, whereby constitutional rights exist only between the government, above, and private actors, below. In other words, only the government is responsible for protecting, respecting, and fulfilling constitutional rights. In many ways, this conception of rights reflects a classical liberal ideology that would maintain a separate, private sphere of liberty unencumbered by the same constitutional duties that bind public actors. Since the mid twentieth century, however, some countries have adopted a horizontal model whereby private actors do have duties – specifically, duties to uphold the constitutional rights of others. Businesses, for-profit hospitals, independent schools, and even private individuals potentially hold some responsibility for constitutional rights, ranging from the freedom of speech to equal protection and nondiscrimination, and even such positive rights as health. In 2017, for example, South Africa’s Constitutional Court decided that landlords had a constitutional duty to uphold their tenants’ right to dignity in their living conditions. This case was not decided on the basis of housing codes or other statutory law, as it would be in the United States, but as a matter of constitutional rights. Thus, within this horizontal conception of rights, private actors live under a constitutional standard and have constitutional duties. The horizontal model – variously called horizontal application, horizontal effect, horizontal rights, or simply horizontality – allows people to articulate cases against other private actors using the language and moral weight of constitutional rights.

This book argues that the practice of horizontality deserves fuller treatment in the academy and beyond. This deeper understanding can be found through the lens of republican political theory – that is, the big-tent tradition of political thought from the classical republicanism of ancient Greece and Rome to the more recent instances of neorepublicanism. A republican theory of horizontality draws on concepts of the common good and duty as touchstones, marking horizontality’s shift away from conventional liberal accounts of individual rights. Horizontality brings to the fore the necessity of limitations on rights, as private actors take on constitutional duties and as more rights come into conflict. As related to republicanism, horizontality can be understood as attempting a kind of democratization of the private sphere, wherein private actors become subject to the same values adopted by the proverbial “we the people” in the constitution. Political debates are unified under a constitutional rubric, and the republican conception of an encompassing common good supplants the ideal of individual liberties.

Rights-Centrism and the Horizontal Shift

In his philosophic investigation of the American Revolution, Morton White explores a revision that Thomas Jefferson made to one of the most famous lines in the Declaration of Independence. In his “original Rough draught,” Jefferson wrote “that to secure these ends, Governments are instituted among Men.”Footnote ¹ This phrasing differs, of course, from the final, more familiar claim that governments are instituted to secure rights. Arguably, this change is not simply stylistic; instead, Jefferson redefines the very role of government as guardian of rights that people already possess, rather than a means to attain ends not yet realized.Footnote ² Later moments in American constitutional history evince similar understandings of constitutionalism, including interpretations of the Fourteenth Amendment that cemented an understanding of the constitution as governing state action only – not private action and perhaps not even state inaction.Footnote ³ This partitioning of accountability between public and private actors tends to take background rules of private law as neutral; private actors are insulated from the commitments the state undertakes in the constitution. Indeed, government is seen as securing rights already acknowledged, and properly refraining from additional projects that risk running up against these rights.

As more countries adopted constitutions in the twentieth century, some followed the practice, at least initially, of limiting most provisions of their constitutions to bind only the actions of the state. After the adoption of the Basic Law in 1949, however, the German Federal Constitutional Court began to apply rights horizontally in its practice of Drittwirkung, or indirect third-party effect,Footnote ⁴ despite some skepticism from some scholars and jurists. The concept of horizontality thus entered onto the scene of global constitutionalism, making it a real option that other courts and constitution-makers might adopt. In turn, legal scholars and practitioners expended much effort to understand horizontality’s effects and limits, as well as to justify this shift in constitutionalism.

With the introduction of horizontality, constitutions no longer aimed only to secure rights, but also to secure certain ends through extending the reach of rights. Robert Alexy elaborates a distinction between the kind of subjective rights that create obligations for particular actors, usually states actors, and objective rights that constitute values of the polity.Footnote ⁵ The rights-centrism that dominated previous conceptions of constitutionalism is thus qualified by the contention that, sometimes, the choices that individuals make under the auspices of private life bear on public commitments.Footnote ⁶ Of course, horizontality still operates in the context of liberal constitutionalism and employs the liberal language of rights. At the same time, it also entails an important shift – a kind of reversal of Jefferson’s amendment to the Declaration – so that the constitution is no longer simply about protecting individual’s rights from state interference, but now articulates public ends common to the polity. Whereas a rights-centric framework, as propounded by many of the social contract theorists of the modern era, tends to comprehend individual obligations merely in terms of what is necessary to secure one’s own rights,Footnote ⁷ horizontality attempts to ground duties in the same substantive principles articulated in a constitution. The move from a vertical to horizontal model changes who is responsible – that is, the very orientation of rights relationships.

While acknowledging the ways in which horizontality runs up against traditional understandings of constitutionalism, constitutional scholarship (and even practice) in the past couple of decades has generally been sympathetic to horizontality. At the time of writing, no fewer than forty-eight national constitutions explicitly state that rights bind private actors.Footnote ⁸ This number does not include the other constitutions that point toward horizontality but depend on the courts to develop it more fully, such as in Germany, or those that provide it only for particular rights, such as in India. Even in the United States, the historic case Shelley v. Kraemer (1948)Footnote ⁹ marks a decision approximating horizontality. In the context of the European Union, Eleni Frantziou maintains that the question of whether to apply rights horizontally ultimately speaks to what “kind of society the EU is setting itself out to be and the values that lie in its core.”Footnote ¹⁰ Since the UK’s passing of the Human Rights Act (HRA), scholars have increasingly asked what rights obligations EU law entails for private entities, culminating in judgments by the European Court of Justice.Footnote ¹¹

Scholars have also argued that horizontality is not a particularly novel innovation in constitutionalism. As Stephen Gardbaum observes, the statement in Article VI that the United States Constitution is the “Supreme Law of the Land” effectively establishes indirect horizontality insofar as the constitution must control the content of private law.Footnote ¹² Moreover, in his book Weak Courts, Strong Rights, Mark Tushnet points out that countries maintain certain “background rules” of private law that necessarily confront – and so already answer – substantive questions about the limits of private action and how public law bears on private relations.Footnote ¹³ In the German context, Mattias Kumm argues that horizontality is just another development in the larger move toward “total constitutionalism” in contemporary law and politics. Denying that horizontality is particularly novel, Kumm sees it almost as inevitable as countries adopt more ambitious socioeconomic rights in their constitutions.Footnote ¹⁴ In light of the questions that horizontality raises for traditional understandings, legal scholars have invested much energy in trying to explain how this phenomenon does or does not comport with the tradition of constitutionalism.

I argue that horizontality should be understood within the republican tradition, which expands the logic of rights to encompass ends and a broader set of citizens’ duties. The constitutional ends that result from horizontality are shared ends – directed toward the common good, with both public and private actors beholden to certain duties. Constitutional actors may still use the language of rights, but horizontality calls for concepts beyond what conventional accounts of liberal constitutionalism typically provide. Indeed, as Kalyvas and Katznelson document, the development of liberalism in the eighteenth century was a reaction to the excesses of republicanism.Footnote ¹⁵ We can, in turn, think of horizontality as a kind of retrospective reaction to traditional accounts of constitutionalism, challenging the neutrality of the background rules of private law and reordering those rules according to public values.

Liberalism serves as a useful theoretical foil to elaborate a republican understanding of horizontality. Horizontality has, however, often been employed as an ameliorative mechanism in nonliberal circumstances – from postbellum America to post-Apartheid South Africa. Something like horizontality might sometimes seem provocative in a largely rights-respecting society that fears limiting rights unnecessarily, but applying constitutional duties to private actors may seem less controversial in an illiberal or more severely hierarchical society. In either case, by applying constitutional principles to create duties for private entities, constitutional agents aim to disrupt existing arrangements and narratives with the republican sensibility that private spaces or actors might somehow be corrected by public values.

Why Republicanism?

The republican interpretation offered here serves as a new lens through which to read and understand the discourses surrounding horizontality. As some of the most telling exchanges and arguments surrounding this topic have occurred in court cases, the main constitutional agents featured here are courts. Nevertheless, this is not primarily a doctrinal account of horizontality, but a theoretical account that builds on constitutional histories. Put differently, the republican framework moves beyond the more common readings that, for example, emphasize doctrine, to uncover the profound questions of political theory that emerge from debates over horizontality: What is the relationship between the individual and the community? What is the nature of freedom? Answers often invoke republican themes that are explored in depth here.

While the argument itself is not normative, criteria and strategies for normative assessments emerge. Considering the history of race in the United States or South Africa, for example, it is not difficult to see the good that might come of applying some rights horizontally when such abuse occurs in private spaces. In such cases, the republican lens highlights more specifically how horizontality transcends rights-centrism in favor of ends of the community. At the same time, the republican lens may reveal a potential for the abuse of horizontality, as well. Authoritarian regimes have frequently invoked such concepts as the common good and civic duty in pursuit of centralized power. The possibility that horizontality might be employed in authoritarian contexts, or even to pass blame for society’s ills onto nonstate actors, is corroborated in legal scholarship.Footnote ¹⁶

Although horizontality reconceives the divide between public and private spheres, this practice generally has not amounted to a complete collapse of public and private, or a total turn to civic republicanism. Horizontality may be conceived as “a republican vein in liberal constitutionalism” in light of the way it operates in constitutional contexts and employs the classically liberal language of rights. Moreover, courts and other constitutional actors generally seek out limiting principles and preserve elements of conventional narratives in debates. In this way, arguments in favor of horizontality run up against other countervailing factors across time, place, and topic. Nevertheless, republican concepts travel in meaningful ways across very different contexts. Indeed, the arguments that diverse constitutional actors across time and place make in favor of horizontality reveal conceptions of community, duty, and freedom akin to those in republican political thought.

Theory and Practice: Plan for the Book

This book’s republican account of horizontality begins first with a theoretical chapter, highlighting the distinction between the traditional vertical model of constitutionalism and the newer horizontal model. Typically, in constitutional theory, the vertical model is understood as rooted in an older liberalism, including stronger commitment to a separate private sphere. On the other hand, the horizontal model possesses affinities with republican thought, including a conception of the polity that is less tied to maintaining strict separation between spheres of life. The chapter connects constitutional practice with some of the core concepts and texts in the history of political thought. Even beyond the relationship between spheres, conversations in political theory about the nature of liberty and the relationship between the individual and community map onto debates about horizontality and its alternatives.

On the horizontal understanding, rights take on a new significance as they become more than mere limitations on government, but also posit prescriptive ends that implicate the polity as a whole. Two key concepts emerge from these observations. Specifically, horizontality gives rise to new calls for parity of public and private spaces according to constitutional values. This, in turn, amounts to a new source of duties for private actors in relation to their fellow citizens. Such concepts as the common good and duty, integral to republican thought, offer a baseline for conceptualizing the parity and duties to which horizontality gives rise.

Subsequent chapters illustrate how these concepts travel in meaningful ways and do similar work across different kinds of contexts, namely the United States, India, Germany, South Africa, and the European Union. Examining constitutional debates, founding documents, and political histories (including case law and statutory law), as well as interviews with practitioners and legal academics reveals how constitutional actors have discussed horizontality in diverse contexts and various areas of rights. While these contexts are different in myriad ways, constitutional actors in each of them have deliberated whether and how to adopt a horizontal model of rights. These deliberations occur across diverse histories and aspirations, institutions and interests, in these constitutional orders and display equally diverse positions in terms of horizontality.

These region-specific chapters are not meant to be “case studies” in the traditional sense of the term. Put differently, they are not included as countries “most different” from each other or “most similar” to each other, so as to control for particular factors in the analysis. These contextual chapters do not explain why courts decide questions of horizontality as they do, or why constitutionalism develops as it does in different countries. Rather, appropriate to this book as a work of constitutional theory, these chapters are illustrative in showing the variety of ends for which and ways in which horizontality has been employed. Likewise, these regions of study cover a range of political and legal circumstances that bolster or obstruct the practice of horizontality in each place. To borrow a turn of phrase from Kim Lane Scheppele, these chapters begin to construct different repertoiresFootnote ¹⁷ for horizontality understood through a republican lens, as these diverse contexts are in different ways considered paradigmatic for the question of horizontality. Through these different paradigms, the book traces threads of republican discourses growing out of debates over horizontality. Republican themes take different forms and occur, to a greater or lesser extent, across issues and constitutional orders, so each context reveals something different about the republican potential of horizontality and the discourses surrounding this practice.

The first four examples may be understood as loose pairings, with the United States and India constituting one pair, and Germany and South Africa another. First, the constitutional experiences of the United States and India are brought into dialogue over the big question of whether their respective constitutions may be applied horizontally. As these countries have grappled with histories of racism and caste, the question of horizontality coheres around questions of equality and antidiscrimination. Republican themes relating to citizenship, fraternity, and the like emerge in arguments from those actors that would prefer something like a horizontal model of rights. In contrast, the experiences of Germany and South Africa are framed as centering around the question of how far the constitution applies horizontally. In particular, the common goal of societal transformation that both these constitutions undertake in one way or another raises questions about how far into private spaces, and to what kinds of issues, constitutional values ought to extend. Republican themes such as obligation to a common good or common morality, and even neighborliness, grow out of these debates.

The framers of the Indian Constitution pursued their practice of horizontality explicitly to avoid the discrimination black persons endured in the United States even after the ratification of the Fourteenth Amendment and its equal protection clause. Likewise, the South African framers pursued their more ambitious version of horizontality to transcend the traditional legal distinctions to which German jurists largely remained committed. Each of these countries had occasion to consider horizontality, and distinct approaches emerged out of the respective constitutional conversations. Taken together, these pairings tell a story of constitutional actors choosing (or not choosing) to transcend the traditional logic of constitutionalism in favor of something different, something more republican. This is not to argue that these entire constitutional orders are or are not republican, only that republicanism describes how people employ and discuss horizontality in what are otherwise complex, multifaceted constitutional contexts.Footnote ¹⁸ In this vein, the European Union serves as an important bookend to these chapters, offering an opportunity to consider horizontality in a supranational context where republican fundaments pertaining to community and citizenship are themselves in question.

The concluding chapter takes up contemporary issues such as the COVID-19 pandemic and Big Tech to consider the status of private actors in constitutional politics and the value of the republican framework in understanding these issues. The conclusion offers preliminary thoughts on the republican framework as a possible guide to determining when horizontality might be applied and how it may be supported, as both a practical and a normative matter. Specifically, constitution-makers and courts might make this constitutional practice more coherent by making it even more republican, perhaps through renewed emphasis on contestation or the legislative function in constitutional politics.Footnote ¹⁹

The Clarity of the Republican Lens

Analyzing crucial constitutional moments – often founding moments when the question of horizontality was debated and, at least initially, decided – lays the groundwork to explore the relationships between these constitutional moments and the governmental institutions that subsequently wrestle with the question of horizontality. Indeed, from these constitutional moments emerge additional questions that various governmental powers – particularly judicial and sometimes legislative – must address. A cluster of relationsFootnote ²⁰ among framing moments and these different powers illustrates how the republican features of horizontality ultimately hold different meanings for differently positioned agents. Challenges emerge in negotiations among institutions as they address questions about horizontality alongside various other considerations. The pull of traditional understandings often perseveres, as constitutional actors acknowledge that upholding rights will require preserving some private sphere. Differing understandings of freedom itself emerge in debates viewed through a theoretical lens of horizontality. Beyond these more theoretical questions, however, a wide range of interests and issues similarly countervail against horizontality across these chapters: persistent racism and the benefits some enjoy from old systems; fear of judicial overstep in policy matters; the financial expense for both private actors and the state; even sheer uncertainty about the practice of horizontality and what role it leaves for other nonconstitutional law and courts.

In light of these and other issues, jurists and other actors will often seek out limiting principles to horizontality or some kind of middle ground. One method is opting for what is called indirect horizontality. On the one hand, direct horizontality allows private actors to plead a cause of action directly against other actors on the basis of the constitution. Judges apply constitutional rights directly to private actors, creating duties to respect, protect, or fulfill the constitutional rights of other citizens. On the other hand, indirect horizontality entails that constitutional principles control the content and interpretation of all areas of law, from legislation to court judgments at common law. Indirect horizontality does not necessarily create obligations for private actors directly, but involves the constitution shaping the law that already regulates private spaces.Footnote ²¹ Recounting these and other arguments uncovers republican-inflected arguments within debates among differently situated agents about the question of horizontality.Footnote ²²

In either the direct or indirect variation, the consequence is that private entities accrue duties as a result of constitutional commitments to certain rights. To this extent, the republican framework speaks to both versions of horizontality. Nevertheless, constitutional framers and actors very often speak as if there were a difference between these approaches, and that the constitutional choice they adopt could lead to different outcomes. In the terms of this book, direct horizontality is taken to encompass a republican logic more fully – specifically in how public commitments bear on private entities directly, with less room for legislatures’ discretion as to how duties are implemented in ordinary law. While important and interesting, the question of whether this distinction matters to case outcomes is beyond the scope of this book.Footnote ²³ However, the chapters that follow demonstrate in the context of specific debates within and across countries how different constitutional discourses seem to adhere to these doctrinal variations. In short, indirect horizontality generally tracks a desire on the part of constitutional framers and other actors to maintain some separation between spheres, whereas direct horizontality tends to accompany a more thorough-going republican logic, an aspiration to shape the polity as a whole according to public principles. Arguably, subsequent chapters reveal the urgency (and resistance) accompanying the direct approach most strikingly in antidiscrimination initiatives across countries. That such doctrinal differences can track different substantive commitments is evinced in comparing, say, the Indian and German constitutional projects, or even South Africa’s Interim and Final Constitutions.

Even when horizontal rights obligations are mediated by private law, constitutional commitments are, in an important way, a source of duties of private actors. Hence, as in the republican tradition, individuals become accountable to the larger projects of the polity, regardless of whether they agree with those projects. In this way, horizontality constitutes something of an innovation of liberal constitutionalism in changing who is responsible for constitutional commitments and in designating the constitution as the source by which individuals are made responsible. This innovation may be justified to the extent that one finds compelling a republican conception of freedom as nondomination. While someone subscribing to the liberal conception of freedom as noninterference may be troubled by the degree and nature of interference in private relations that horizontality entails, one who maintains a republican conception of freedom as nondomination may be more inclined to recognize horizontality as leveraging the same constitutional principles that protect people from domination by public entities (imperium) to protect them also from domination by private entities (dominium).Footnote ²⁴

Some of the most heated debates occur around questions of equality and duties within the private sphere. Such matters are pressing in the United States and India, where debates about horizontality have focused on equality and antidiscrimination provisions.Footnote ²⁵ Matters of equality and antidiscrimination figure into the German and, especially, South African practices of horizontality as well, raising questions about how far horizontality reaches into certain corners of private life, as both countries aim for transformation. Should equality itself apply horizontally, the German Federal Constitutional Court finally asked in the 2008 Stadium Ban case?Footnote ²⁶ Might private actors have duties with respect to positive rights that aim at a substantive form of status equality,Footnote ²⁷ the South African Constitutional Court asked in Daniels v. Scribante?Footnote ²⁸

That the horizontality of rights related to equality would be contentious across contexts is not surprising. Rights related to equality are often conceived as part of a larger constitutional project and, thus, as demanding more of the duty-bearers, be they public or private actors. And when private actors are in fact the duty-bearers, the resultant limitations on rights and liberties enjoyed are felt more acutely in that they intervene more directly in private life.Footnote ²⁹ In short, equality cases seem to be perceived as demanding more positive action of private actors. Thus, while the German Lüth case applying freedom of expression horizontally simply requires that an individual face what economic harm may arise from calls for a boycott,Footnote ³⁰ the Indian Medical Association case applying affirmative action requirements to private actors actually involves revising existing systems and programs.Footnote ³¹

Conclusion

Scholars across disciplines have long argued the interconnectedness of public projects and private decisions, specifically how private actions may bear on public projects – from Legal Realists and Critical Legal Studies scholars maintaining, in Mark Tushnet’s words, “that ‘private’ property is actually a delegation of power from the state,”Footnote ³² to the famous feminist refrain that the personal is political.Footnote ³³ Robust welfare states, antidiscrimination statutes, and an array of other arrangements implicitly concede this connection and suggest, on some level, that citizens have some obligation to public projects and to each other. With the introduction of horizontality in constitutionalism and attendant calls for parity among spheres and for citizens’ duties to uphold constitutional commitments, this connection between private behavior and public projects becomes more explicit.

In horizontality, ideas from republican theory prove to be alive and quite relevant in constitutional politics. The claim is not that this tradition plays any significant role in these episodes from constitutional politics as a historical matter, nor is the goal to write off more conventional liberal narratives as irrelevant to horizontality. Rather the aim is to highlight the presence of republican elements in discourses surrounding horizontality. Whether or not particular arguments for horizontality prevail in law and politics, teasing out their republican themes imbues these debates with new significance and serves as a call to appreciate the full significance – in scholarship and practice – of horizontality. Moreover, the republican perspective offers new opportunities to assess institutional struggles pertaining to horizontality. Republican themes arise, for example, in considerations surrounding the role of courts, divisions of power in federal arrangements, the allocation of issues in a supranational union, and in constitutional assemblies aiming for transformation. Thus, while arguments for horizontality may sometimes seem new or surprising from a modern perspective emphasizing rights over duties, the republican lens reveals ways in which these discourses ultimately participate in conversations that are longstanding and not soon ending.