The concept of authority has diverse and highly contested meanings across disciplines such as philosophy, sociology and political science.Footnote ¹ The indeterminacy inherent to this concept has made its use in international legal scholarship and practice fraught with difficulty.Footnote ² Nevertheless, this volume is the pièce de résistance of a project that bravely and successfully took on the daunting task of delineating it in a way that reflects the plurality of its usages in international law. It has also turned this concept into a tool to study international courts (ICs) through a comparative framework.

International Court Authority is structured in three main parts and concludes by ‘reflecting on the lessons learned from studying how contextual factors influence the variable authority of ICs’.Footnote ³ First, the volume elaborates a framework, built around the concept of de facto authority, as a tool to study the functioning of ICs in the international legal order. Second, the volume presents the empirical heart of the project which invites contributors to use this framework to study specific courts and tribunals. Third, the volume engages with it in a critical manner, inviting contributions of different disciplines to reflect on the salience and value of the framework and its theoretical underpinnings.

This review will begin with a brief summary of the framework, focusing on Part I, exemplifying its application and effect with case studies from Part II. The review will then shift focus to two reflections in relation to the methodology and working assumptions. Finally, it attempts to place the contribution of this volume in the broader international legal scholarship on ICs.

In Part I, the editors set out a framework to study ICs, carefully chiseling away superfluous aspects of the concept of authority in order to sculpt an empirical tool that can be used to assess different ICs comparatively. The editors acknowledge the existence of diverse conceptualizations of authority and briefly discuss four such approaches in relation to ICs specifically. These approaches encompass legal formalism, normative legitimacy, sociological legitimacy, and compliance studies and performative approaches. The editors distinguish their own approach as ‘practice based’, drawing from the practices of key audiences and how these constitute IC de facto authority. The audience is understood as (potential) litigants, governments, judges, and larger constituent communities (e.g., lawyers, scholars, NGOs). The editors explain that:

The proposed metric, they contend, is purposefully agnostic to the motives or reasons why an audience recognizes an IC’s authority.Footnote ⁵ Rather, the editors explain that the approach is to empirically observe practices in order to investigate how contextual factors shape them and how they account for the variation in IC authority across different audiences. They consider that their approach differs from sociological legitimacy, which focuses on how the subjective perceptions of an audience legitimize ICs and how they justify IC practice and power. In addition, their notion of authority is distinguished from normative legitimacy since ‘a court can do everything normative theorists expect of a legitimate international judicial body and still not possess authority in fact’.Footnote ⁶

The proposed measure of de facto authority is the conjunctive standard of (i) recognition of the obligation to comply with a court’s rulings; and (ii) engaging in meaningful action towards giving full effect to those rulings.Footnote ⁷ In this sense, the methodological framework looks at the practices of key audiences (public statements, conduct, and other observable behaviour).Footnote ⁸ The framework proposes a five-level metric, from no authority to popular authority, where the decisions trigger action from the public at large.Footnote ⁹ Each of these levels exist independently from the other. The levels correspond to the practices of key audiences and are based on how the audience meets the conjunctive standard of recognition and meaningful action in response to the IC rulings. For instance, Leslie Vinjamuri finds in Chapter 14 that the ICC gathers extensive authority,Footnote ¹⁰ especially with civil society organizations, for what it is, and the principles and commitments that lie at the heart of its creation. On the other hand, the ICC fails to elicit narrow authority,Footnote ¹¹ that is it lacks state support for what it does in practice.Footnote ¹²

The variations observed in practice are explained by looking at the contexts in which ICs operate (legal, political and institutional) under the hypothesis that factors exogenous to the court influence the conduct of the audiences.Footnote ¹³ The authors discuss three broad categories of contexts. These categories assist in explaining the differentiation in audience engagement with IC rulings. The first of these categories are institution specific factors. They include the way a case can be brought to the court (e.g., self-referral versus UNSC referral for the ICC in Chapter 14) or the subject matter competence which brings about differing authority, this is the case for instance with Islamic law states in disputes before the ICJ where authority differs on whether the case involves diplomatic immunity or territorial disputes (Chapter 12). Second, there are factors related to the constituencies and their varied interests. A clear example of these factors is the case of the Southern African Development Community (SADC) which suffered severe backlash from the Zimbabwean government, a key constituency, eventually leading to its dissolution (Chapter 6). Third, there is the influence of global, regional, and domestic contexts. These can be observed, for example, in the different historical contexts in which the prosecutors of international criminal tribunals were operating. The regional contexts looked differently in the post-Second World War occupation vs post-cold war period, thereby yielding different types of authority (Chapter 15).

A reflection on the methods underlying this volume must start by noting that it is based on an iCourts project that spanned several years and demonstrates a clear editorial direction. This is further reflected in the editors’ own substantive contributions to the volume. The work has been subject to multidisciplinary discussions which present both insightful contributions as well as their methodological, theoretical shortcomings, an accomplishment that assuredly needs to be applauded. This volume is also exemplative of the aspirations of international law as a science, or the ‘scientification’ of international law.Footnote ¹⁴ Rooted in nineteenth century ideals of science as a tool to produce objective universals,Footnote ¹⁵ these aspirations contemporaneously take on the form of ‘multidisciplinary modes of reasoning and the appeal of the conceptual, descriptive and evaluative tools of social sciences’.Footnote ¹⁶

The framework, or ‘metric’, developed by this volume falls squarely within this ‘scientification’ effort – an effort that may prove valuable within clearly prescribed limits. An example of these limits is noted in Chapter 9 on the Inter-American Court of Human Rights (IACtHR), where Alexandra Huneeus describes the authority framework as a typology, which places focus on the type of authority and in the process, leaves out a meaningful insight on the actual power yielded by the IACtHR.Footnote ¹⁷ In this volume, ‘scientification’ is also reflected in the editors’ proclaimed agnosticism of the authority framework as to the motives of audiences in response to IC authority. From one perspective, this move creates a certain level of objectivity: the framework measures but does not judge. In this way, it can be employed across ICs and contexts thus basking in the profession’s never-ending quest for universals.

Yet, this agnosticism is also criticized in Part III of the volume as well as in some of the empirical chapters in Part II. In Chapter 6 on the SADC for instance, E. Tendayi Achiume acknowledges the usefulness of looking at the practices of key audiences to understand IC authority, but she questions the ‘agnostic’ feature of the editors’ framework.Footnote ¹⁸ The metric fails to adequately establish a comprehensive relationship between contextual factors and IC authority, as such an approach would require ‘reckoning with subjective beliefs, perceptions, and motivations underlying key audience practices’.Footnote ¹⁹ E. Tendayi Achiume contemplates the costs of the framework’s agnosticism and suggests the need for the further exploration of these costs, which, she concedes, ‘may be outweighed by the simplicity and broad applicability of a framework that focuses only on audience practices’.Footnote ²⁰

Though the framework is flexible and dynamic, it cannot be fully agnostic, not least by virtue of the positionality of the framework’s creators.Footnote ²¹ The editors explain in their introduction to Part IIIFootnote ²² that they are not themselves agnostic,Footnote ²³ rather the metric is agnostic. They agree that actor motives are important yet doubt the extent to which we can know these motives, referencing Max Weber on the reasons why individuals respond to authority.Footnote ²⁴ Hereby, the editors position their work within an epistemological tradition that observes, describes, and analyses, yet does not seek to offer a comprehensive explanation of behaviours as this would not be fully knowable. Admittedly, contextual factors may be more easily observable than motives and thus better at determining influencers of behavior. Yet one could argue that context as readily as motive may also not be fully knowable.

One element that is missing in the volume is the role of procedure and court practice in yielding authority,Footnote ²⁵ especially since rules of procedure may dictate the extent to which actors may have engaged with the court and its decisions. While one may posit that procedural questions form part of the institutional context explaining the varying degrees of authority, this line of thinking is swiftly brushed aside in the first chapter under the working assumption that ‘ICs follow common and recognizable procedures associated with the rule of law’.Footnote ²⁶ In Chapter 18, Michael Zürn objects to the distinction made between authority and legitimacy and hints at the absence of consideration for process in the framework. He considers that ‘de facto authority or legitimacy are not generated in a vacuum but formed in a context of ongoing contestation of societal beliefs and norms about the appropriate exercise of authority’.Footnote ²⁷ He implies that it is necessary to look at the process and that the way in which authority is generated is important. Curiously, however, he notes that ‘highly technical access rules and rules of procedure prevail’ which ‘provides a protection layer for courts and makes the politicization of the decision-making process unlikely, processes of legitimation and delegitimation most often focus on the content of these judgments’.Footnote ²⁸ As a result, he comes back to the working assumption of the volume’s editors building on a narrative of procedure as a mechanism that appears technical, objective, and depoliticized in nature. The centrality of the outcome, of the external, binds most of the scholarship on ICs, and is reflected in this volume as well. Such an approach, however, leaves out an account of the way in which power is exercised by judicial elitesFootnote ²⁹ and what role procedural practice plays in this process.

To conclude, this volume fits in a broader context of recent scholarship that reflects the proliferation of ICs in the past decades.Footnote ³⁰ This scholarship moves away from discussing dispute settlement bodies as a side product of a substantive field of law. It looks to identify commonalities and cross-fertilization between ICs. It looks at ICs as a subject of inquiry in its own right, and perhaps also to the role of international lawyers and academics’ imaginaries in constituting ICs.Footnote ³¹ In doing so, the scholarship largely follows the path of ‘scientification’ of international law,Footnote ³² and its obsession with IC rulings, which omits any engagement with the critical role of practice and procedure. These observations on the broader scholarship are also this review’s two main reflections about the volume. While the structure of the volume in Part II remains organized along specific courts, the overall project aims higher and forms an example of the evolution of knowledge on ICs and the way they are studied. This results in a metanarrative that binds together this vast group of institutions, complementing the ongoing theorization efforts on ICs. Thus, the work also discusses how ICs are distinct from other international institutions, in particular when speaking of authority. These arise due to the different expectations associated with judicial institutions: the particular procedures and presumed a-political nature of ‘deciding’ based on the application and interpretation of norms rather than arrival at a compromise.Footnote ³³ Additionally, ICs are distinguished from domestic courts due to their default authority status: domestic courts presumably possess the authority which ICs as a matter of principle lack.Footnote ³⁴International Court Authority offers a framework, and perhaps a starting point, for a new theory, on how these courts and tribunals exist or function in the international legal order by assessing their influence through the concept of authority. Part III of the volume, which represents a critique of the framework, comes closest to engaging with the theorization of ICs. This remains very much a work in progress.Footnote ³⁵ What makes this book essential reading for students and scholars interested in ICs is the defined focus on context. While it may seem self-evident that ‘context matters’, the editors rightly point out that the scholarship on ICs has so far failed to take this into account in a significant and comprehensive manner. In any event, this volume is a valuable contribution to ICs scholarship rendered more remarkable by the authors convincing, in-depth empirical studies.