—Christina R. Bambrick, Filip Family Assistant Professor of Political Science, University of Notre Dame
[Editor’s Note: ICONnect is pleased to feature a symposium by the five nominees for this year’s ICON-S Book Prize. This is the fourth entry in the symposium.]
Christina R. Bambrick, Constitutionalizing the Private Sphere: A Comparative Inquiry. Cambridge: Cambridge University Press, 2025.
Recent years have offered stark reminders of the power that private actors exercise in a polity. The COVID-19 pandemic revealed the extent to which individual choices impact public health, while elections in democracies around the world have laid bare big tech’s vast influence over politics. These and other developments give new urgency to the question of horizontality—the idea that constitutional rights create obligations not only for the state but for private actors as well.
My book, Constitutionalizing the Private Sphere, considers the theoretical implications of adopting a horizontal model of constitutional rights. I argue that horizontality, or horizontal application, may be understood through concepts from republican political theory. On a horizontal understanding, rights are no longer simply limits on government, but take on new significance as ends that implicate the broader polity, including private actors. Examining horizontal application through the lens of republican thought uncovers this theoretical significance: republican concerns about nondomination, the common good, and civic duty echo in constitutional discourses, and suggest changes to constitutional practice in ways that doctrinal analyses do not fully capture.
THE EMERGENCE OF HORIZONTAL APPLICATION
Legal scholars and jurists have traditionally understood private law as the proper means by which to regulate private actors. In this understanding, the law governing the private sphere is more or less independent of the constitution. Likewise, the constitution remains primarily a source of government’s obligations, with rights such as the freedom of speech or the right to education triggering duties only for state actors. However, a 1958 judgement of the German Federal Constitutional Court charted a different approach. In the Lüth case, the Constitutional Court viewed Germany’s newly enacted Basic Law as not simply an instrument to limit state power, but as articulating an objective order of values to shape even the broader reaches of society. The constitution could not be confined to any particular sector but “radiated,” in the Court’s now-famous phrase, across all spheres of law and life.
With the horizontal application of rights, a constitution becomes a source of obligation for more actors across the polity—from businesses and hospitals to private schools and individuals. In some ways, this horizontal shift seems to be a natural development in constitutionalism. Increasing commitment to socioeconomic rights, for example, will likely bear on actors beyond the government. A right to have access to adequate housing may come to involve landlords, perhaps obligating them to ensure dignified living conditions for their tenants, as the South African Constitutional Court ruled in Daniels v. Scribante (2017). Even while the horizontal application of rights may be part of a longer predictable trajectory, it marks a shift in how we think about the very purpose of constitutions, a shift that calls for a deeper theoretical account.
A REPUBLICAN ACCOUNT OF HORIZONTALITY
My book argues that we can understand this shift in constitutional practice through the lens of republican political theory. This is not to say that constitutional actors are themselves informed by republican theory when they adopt horizontal application. Rather, certain concepts of republican thought, from Greco-Roman variants through the neo-republicans, enter into these constitutional debates on the obligations of private actors. Republican theory recognizes that freedom, understood as nondomination, may be threatened by both public and private agents. In Philip Pettit’s neo-republicanism, for example, an employer who wields arbitrary authority over employees threatens freedom as much as any abusive state. Horizontal application carries the same insight as such republican understandings, namely, about the power that private actors often have to realize or jeopardize constitutional commitments.
The book goes on to elaborate two additional features of horizontal application that map onto republican theory. First, horizontality effects a new parity across spheres of life and law. In adopting horizontal application, constitutions address the broader polity more directly and thereby become articulations of something like a common good. The concept of the common good recurs through republican thought. It is generally defined as that which is good for a community as such, as opposed to what is simply in one’s individual interest. The common good encompasses an appreciation that spheres of public and private life are not to be divided facilely, since the “res publica” ultimately affects everyone. In a similar way, horizontality addresses conventional understandings of the public-private divide, responding with a model that brings a broader range of people and entities into the public project.
Second, emerging from this parity comes a new notion of duty, another essential concept in republican thought. By making the constitution a source of obligation for private actors, horizontal application brings the language of duty where rights talk has traditionally dominated. That said, the duties that result from horizontality are not necessarily identical to the constitutional duties of the state. Most private actors have fewer resources at their disposal than does the state, so could not be expected to assume the same levels of obligation to uphold constitutional rights, even if people wanted them to. An individual landlord will have fewer resources than the state, in contrast with large technology companies whose influence and access to information rival that of many states. Accordingly, there remains room to distinguish between different kinds of nonstate actors, even as private entities accrue constitutional duties.
A COMPARATIVE INQUIRY
The book advances its republican account of horizontal application through the experiences of the United States, India, Germany, South Africa, and the European Union, treating the first four as loose pairings. Considering the United States and India alongside each other is productive as constitutional actors in both places debated whether their respective constitutions would apply horizontally at all. As they grappled with histories of racism and caste, the question of horizontality cohered around questions of equality and antidiscrimination. In the United States, the state action doctrine set the terms of debate over the reach of equality into privately-owned spaces as early as the Civil Rights Cases (1883). By contrast, the Indian framers chose to adopt explicit horizontality provisions related to equality and antidiscrimination in the 1950 Constitution, in a conscious effort to circumvent the difficulties the United States faced. Republican themes relating to citizenship, fraternity, and the like emerge in arguments from actors in both contexts that preferred a horizontal model of rights.
Constitutional debates in Germany and South Africa highlight the question of how far the constitution applies horizontally. The common goal of societal transformation that both constitutions undertake raises questions about how far into private spaces, and to what kinds of issues, constitutional values should extend. While the German Constitutional Court recognized the Basic Law’s transformative project in the wake of World War II, it continually operated in a specialized legal system in which private law previously enjoyed broad autonomy. The German doctrine on horizontality thus worked primarily through indirect horizontal effect. With an eye to the limits of the German doctrine of indirect horizontality, the South African constitutional framers were determined to root out the vestiges of apartheid across spheres of life, and so included provisions for both direct and indirect forms of horizontality in the Final Constitution. Republican themes such as obligation to a common morality and even neighborliness grow out of debates in these contexts, with an overarching consensus that transformative constitutional projects cannot but implicate the private sphere.
The European Union’s experience serves as an important coda 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. From the Defrenne (1976) case on equal pay to more recent cases like Bauer et al. (2018), the Court of Justice of the European Union has progressively extended horizontal direct effect across Treaty and Charter rights. Through this history, the question of horizontal application has been intertwined with the broader issue of European integration, bringing into sharp relief the deeper republican stakes of this debate.
THE CLARITY OF THE REPUBLICAN LENS
The republican themes in discourses surrounding horizontality demonstrate the paramount importance of this constitutional question. It is no coincidence that debates about horizontality often emerge when polities are grappling with past atrocities. Slavery in the United States, caste and religious discrimination in India, genocide in Germany and Europe more generally, apartheid in South Africa—each society has a past that persists in the present, with which constitutional actors must grapple. And indeed, constitutional actors in each place contemplated horizontality to overcome social disharmony, invoking republican concepts of rights and duties, fraternity, and the common good in the process. Taking this book’s republican framework and comparative examination together thus demonstrates a crucial insight: while we may certainly speak of separate public and private spheres, the gravest social ills can only be confronted by the polity as a polity. Although arguments for horizontality may sometimes seem new or surprising from a modern perspective emphasizing rights over duties, the republican lens reveals how debates over horizontality participate in conversations that are longstanding and not soon ending.
Suggested citation: Christina R. Bambrick, Constitutionalizing the Private Sphere: A Comparative Inquiry, Int’l J. Const. L. Blog, Jun. 30, 2026, at: http://www.iconnectblog.com/constitutionalizing-the-private-sphere-a-comparative-inquiry/