The 2001 International Law Commission (ILC) Draft Articles on Responsibility of States for Internationally Wrongful Acts (ILC Articles) left open many aspects of the question of State responsibility for breaches of obligations owed to a group of States or the international community, having struggled to reach a consensus on the issue. The past two decades have witnessed theoretical and practical developments on specific topics such as obligations erga omnes, actio popularis and third-party countermeasures, but there has been no comprehensive research addressing the entire regime of State responsibility.
Sarah Thin’s new book, Beyond Bilateralism: A Theory of State Responsibility for Breaches of Non-Bilateral Obligations, is a timely and substantial contribution to this field. As the first of its kind, this book promises to offer ‘a comprehensive model for the international legal responsibility for breaches of non-bilateral obligations’ (13), providing insights into theoretical foundations, the legal regime, adjudicative practice and the international legal system more broadly.
From the outset, the scope of the book is carefully delineated as ‘non-bilateral responsibility’ (7). Thin’s choice of terminology here is prudent and commendable, as existing literature typically employs terms such as ‘community interests’, ‘obligations erga omnes (partes)’ and ‘jus cogens’ in an inconsistent and chaotic manner. Thin provides further clarity by dividing non-bilateral obligations—those whose breach gives rise to non-bilateral responsibility—into ‘structurally non-bilateral obligations’ and ‘community interest obligations’ (3–6, 52–67). These categories can overlap in substance, but they diverge from the bilateralist model for different reasons: the former cannot break their legal relationship into separate bilateral pairings, while the latter encompasses community-related significance. This typology lays a firm foundation for the subsequent analysis.
The main body of the analysis spans Chapters 2 to 5. In Chapter 2, Thin proposes an objective theory of non-bilateral responsibility. Rather than examining responsibility directly, she begins with a thorough analysis of basic ideas of interests and obligations in international law. She highlights that developments in international environmental law and the protection of humanity demonstrate that ‘international law now protects common interests more than ever’ (39). The protection of such interests gives rise to non-bilateral obligations, and breaches of these obligations result in non-bilateral responsibility.
In contrast, bilateral obligations protect only individual interests existing exclusively between two States. The same principle applies to the bilateral model of responsibility, where one State’s responsibility is owed solely to another. If the injured State chooses not to invoke it, the wrongdoing State faces no legal consequences. In other words, invocation of responsibility is a subjective right of the injured State. This subjective model proves incompatible with non-bilateral obligations and responsibility. The author convincingly argues that non-bilateral responsibility cannot be conceptualised as ‘a subjective legal relationship or an adapted version of bilateral legal relationships or responsibility’ (73). Instead, she puts forward an ‘objectivised theory of international responsibility’ (81). Under this framework, wrongfulness and responsibility are not contingent upon the subjective rights of a State to whom the obligation is owed but, rather, are determined objectively based on the legality of the conduct. While the argument for the inapplicability of bilateralist theory is well reasoned, this chapter feels slightly unbalanced, as the new objective theory is presented rather briefly.
In Chapter 3, Thin tests and applies this objective theory to the operation of non-bilateral responsibility. This includes an examination of the origins of responsibility (particularly the concept of injury), the preclusion of wrongfulness, waiver and acquiescence, the content of responsibility and its implementation and enforcement. By employing the objective theory, Thin’s analysis makes a significant contribution to clarifying the legal regime of non-bilateral responsibility which the ILC Articles did not address in detail. For instance, she argues that, as a circumstance precluding wrongfulness, the injured State’s consent ‘would preclude only invocation by the injured State, rather than removing the wrongfulness inherent in the act itself’ in the context of non-bilateral responsibility (101). This chapter relies on deductive reasoning from scholarly discussions as well as the ILC Articles and commentaries. Certain sections, such as those on community interest countermeasures, are somewhat cursory and would have benefitted from further elaboration.
Chapter 4 focuses on the function of the objective theory of non-bilateral responsibility in international adjudication. The author examines three international judicial bodies—the International Court of Justice, the International Tribunal for the Law of the Sea and the World Trade Organization Dispute Settlement Mechanism. Through an analysis of their procedural rules and judicial decisions, she concludes that their procedural frameworks are ‘broadly compatible with an objective theory’ (186). Nevertheless, their practical approach is ‘mixed’ (187). Thin advocates a new conception of the judicial function, one ‘rooted in notions of legality and compliance, rather than merely dispute resolution and the reparation of injury’ (187).
In Chapter 5, the author explores the broader implications of non-bilateral responsibility for the international legal order through the concept of ‘publicness’. She argues that recognising non-bilateral responsibility represents a ‘public shift’ in international law, which is traditionally understood as a system rooted in private law (191). Drawing on domestic legal theories, Thin identifies four elements of publicness: community, universality, hierarchy and objectivity, and demonstrates their relevance to international law. Linking non-bilateral responsibility with publicness not only helps to fill gaps in the rules on non-bilateral responsibility but also shows how public law principles such as transparency and democracy can be ‘operationalised’ through non-bilateral responsibility (228).
The book is well structured, progressing from theory to doctrine and practice, and concluding with a reflection on general international law. The author’s writing is accessible and engaging, and she excels at using examples to illustrate abstract rules of State responsibility. The book adopts a doctrinal approach and analyses lex lata. This works well in Chapter 4 where judicial practice is examined, but Chapter 3 would have benefitted from a deeper analysis of State practice and the historical evolution of the law, which is at present limited and unevenly distributed across the sections.
In summary, Thin has successfully defined a category of non-bilateral responsibility in international law and offered a compelling framework for systematising this area of responsibility. This book undoubtedly provides the foundations for a new field of analysis in international legal responsibility. Moreover, given that international society is currently facing a concerning number of serious breaches of international law, such as Russian aggression against Ukraine, Thin’s analysis of the relevant rules is of significant value for both States and international courts and tribunals.
