Jeffrey Dunoff and Mark Pollack's edited volume takes stock of the rapid rapprochement between International Law (IL) and International Relations (IR) in the course of the last twenty-five years, mostly in North American universities, which has led to a myriad of promising studies. The twenty-six chapters that compose Interdisciplinary Perspectives on International Law and International Relations are written by some of the field's leading researchers from both disciplinary backgrounds, and aim to “assess critically the value-added (if any) of IL/IR to our understanding of international law, as well as to identify IL/IR's lacunae, biases, and blind spots” (p. 4). The book succeeds remarkably well in balancing different schools of thought (institutionalism, liberalism, constructivism, and realism) and different methodologies (for instance, theoretical and empirical studies, the latter including both qualitative and quantitative). It constitutes a comprehensive and timely state-of-the-art discussion of the current debates. Therefore, this book is bound to become a source of reference for researchers and students of the two disciplines, or, otherwise, compelling reading for anyone interested in international studies.

A thread of the book is that, as Jana Von Stein puts it, “IL and IR scholars are talking to each other with much greater frequency now than they were even a decade ago” (p. 495). Yet the editors note at the outset that this “trade” has largely been asymmetrical: IL/IR writings consist “primarily of the application of the theories and methods of political science as a discipline to the study of international law as a subject” (p. 10). They add that “asymmetrical terms of trade have given rise to significant interdisciplinary tensions” (p. 10). While Richard Steinberg sees realism as “the theory international lawyers love to hate”, Dunoff and Pollack submit that IR scholars are also prone to “caricature and ignorance” (p. 13) in their treatment of international law. To doctrinal international lawyers who “aim to insulate legal analysis from politics (Kenneth W. Abbott and Duncan Snidal, p. 40), IR studies are an unpleasant reminder of the social grounding of IL.

Yet each discipline has apparently contributed to the debate on the basis of its comparative advantage. IR has offered the method of a social scientific analysis that international lawyers lacked, including solid conceptual bases. IL scholars, on the other hand, have provided doctrinal analyses and knowledge of the law. Throughout the book, most chapters first identify an IL phenomenon or an issue (e.g. the development of soft law, the multiplication of international courts, or the limits to enforcement in international law), and then show how IR can contribute to our understanding of this phenomenon or issue. As a result, they are fundamentally political analyses of international law.

That being said, the author's institutional affiliation does not constrain the type of analysis. The volume is replete with examples of works by international lawyers engaging in IR analyses and IR scholars with a deep understanding of IL. This has allowed genuinely transdisciplinary debates to develop. Regarding legitimacy, for instance, Daniel Bodansky shows that “[i]n many cases, the work of international lawyers and political scientists … is virtually indistinguishable” (pp. 322−3). Similarly, Jana von Stein considers that it “would be inaccurate” to distinguish broadly between IR and IL approaches to compliance, as debates transcend the disciplinary borders (p. 478).

IL/IR studies have great potential to improve our understanding of IL. It is a compelling point, for instance, that international law should be tailored “to an accurate assessment of which laws are likely to be viable, effective, and dynamic, given underlying social constraints” (Moravcsik, p. 111), and that IR offers the methodologies for doing so.

Interdisciplinarity may, however, lead to some misunderstandings. Anecdotally, the word “positivist” is used in the book in two different meanings—“in Comte's scientific sense of the term” by IR scholars, and in “the Austinian jurisprudential sense” by IL scholars. More importantly, Lisa Martin shows that IR scholars have often misused the concept of compliance; she identifies compliance to be “a legal concept that is unusually ill-suited to the central social-scientific pursuit” (p. 591). According to Martin, political scientists using compliance data to measure the effectiveness of international law “make errors of both omission and commission—mistakenly attributing state behavior to institutional participation, and underestimating the influence of institutions on states that are not ‘in compliance’” (pp. 591−2). She concludes that “the way that compliance has entered the IR literature is a cautionary tale about the risks associated with celebrating interdisciplinarity without careful attention to the different demands and purposes of various disciplines” (p. 606). Anne-Marie Slaughter argues that such obstacles may be solved through the growing socialization of IL and IR scholars, and the development of team works (pp. 613−14). Joost Pauwelyn and Manfred Elsig's chapter on the politics of treaty interpretation reflects the beneficial symbiosis between a thorough doctrinal investigation and a solid IR analysis (p. 445).

Besides such terminological and conceptual obstacles, another hurdle stems from the sociological tension alluded to before. This tension is perhaps the fruit of a feeling of competition between IL and IR, as well as disciplinary isolation. Jutta Brunée and Stephen Toope note that “relatively few international lawyers have taken advantage of [constructivist] contributions, perhaps because constructivism is a poor fit for those who see the legal status of a norm as exclusively connected to its provenance from a formal source” (p. 129). They add: “constructivism can speak to international lawyers only to the extent that they are prepared to understand legal norms as social norms, and so as constituted and powered primarily by social practices” (p. 129). Despite significant progress, IL/IR studies often remain affected by rigid departmental isolation and diverging disciplinary agendas. As almost all the contributors to this book are based in North America, one may wonder whether such hurdles have been overcome at all in other regions of the world.