In Islamic Law and International Law: Peaceful Resolution of Disputes, Emilia Justyna Powell argues that the domestic legal systems of “Islamic Law States” (ILS) shape engagement with the dispute resolution mechanisms offered in the international law system—but not all in the same way. The work offers both a theory “draw[ing] a direct link between laws within states and laws regulating interactions between states” (p. 48) and a rich empirical investigation. Both elements will be extraordinarily valuable to scholars of international law and international relations who wish to take domestic legal systems seriously but who are not specialists in Islamic law: the study renders a very complex subject accessible without oversimplifying it. Moreover, it corrects two prominent shortcomings in many nonspecialist treatments of Islamic law: the tendency to treat particular rules in decontextualized isolation and the tendency toward poorly grounded overgeneralization. Powell’s study is notable for its careful depiction of complexity within the broad Islamic legal tradition, as well as variation across both countries and time. To take such a descriptively rich and conceptually careful approach and still be able to create a useful empirical study of the category “Islamic Law States” is a remarkable and important accomplishment.

There are elements of the description and analysis that scholars of different specializations might argue about, like the degree to which Western governance systems are entirely secular or whether judicial review is inherent to Western constitutional systems—but this is true of any sufficiently complex work and a natural part of making a useful contribution to scholarly debate. One might also debate Powell about the best way to conceptualize and account for the diversity of Islamic legal tradition without broadening the “Islamic law” category back out to something more like “Islamic country”; however, she is laudably careful to note that Islamic law cannot responsibly be treated as merely a collection of rules and takes seriously the task of constructing a positivist approach that does not fall into this error. Because the definition of Islamic law is essential to the framing and empirical work of her study, and this subject is unfamiliar to many readers outside the Islamic studies field, an explicit conceptual map of the legal tradition, legal system, shari’a, and other concepts might have been welcomed to signpost the route through what the author notes is complex and disputed territory.

The depiction of diversity and commonalities in Islamic legal systems is by itself a valuable contribution of the work and will render Islamic law in modern states both better understood and more accessible to study by scholars from other fields. This qualitative descriptive work is an important underpinning of the later empirical chapters; Powell does not treat Islamic law in domestic systems as merely a question of “how much” is present in a system, but of the types and arenas in which Islamic law variously operates across all ILS cases. Applying this specifically to the use of territorial dispute resolution mechanisms, for example, she argues that the “specific configurations of Islamic law and secular law within ILS have vital effects on these states’ choices of conflict management venues in territorial disputes” (p. 201). This is, as she points out, an advantage of an approach that does not treat “Islamic” as a single variable.

Powell stresses the point that all of these systems combine both Islamic and non-Islamic law, with secular law overwhelmingly drawn from the civil law tradition. Yet the concept of legal pluralism does not seem to appear in the study; its omission is a curious choice, because this concept might usefully have informed the analysis of domestic legal systems by casting light on the reasons for variations in the degree and type of Islamic law across cases. Powell notes that the historical “gradual weakening of traditional Islamic law was largely caused by the emergence of a Western-educated legal elite” (p. 52), but this development was not merely a choice of domestic systems; it was to a large degree a product of colonialism. The role of colonialism in shaping domestic law is mentioned only in passing, and its more thorough treatment would help undergird the analysis of how and why Islamic law is important to domestic systems.

Powell offers a careful comparison of the similarities and differences between Islamic and international law, addressing both substance and procedure. The “partial consonance” between the two bodies of law is explored to demonstrate that shari’a and international law are both drawn together in some ways by similarity and rendered incompatible by others. This chapter builds a sound foundation for the later empirical analysis of how and why the ILS vary in their use of mechanisms of international law; it also undergirds the larger point of the book—that grand generalizations about Islamic law, so often seen in policy and political discourse, are poor guides to understanding either law or politics. Powell’s careful treatment of legal complexity includes a chapter considering the effect of both various jurisprudential schools of Islamic law and regional variation; interestingly, she finds that the dominant school of Islamic jurisprudence in use in a country does not affect ILS’ views of international dispute resolution mechanisms, but that regional variations do. Powell also takes into account the nonlegal political factors that shape the use of international conflict resolution venues. Islamic Law States are, like other states, faced with uncertainty in the international law system, differ as to their power and preferences in a given dispute, and so on. The book consistently applies the assumptions and methods of social science to countries that have in the past often been exoticized or treated as problematic cases; this strengthens her empirical analysis and the weight of her findings.

The contributions of this book are many, for scholars in a range of fields. It is not written to be an introduction to Islamic law in modern states, but it fills that purpose well for political scientists. International relations scholars and practitioners alike should take careful note of the admonitions of the final pages, which are well grounded in the foregoing research: “One cannot set aside Islamic law as unimportant to modern interstate interactions” (p. 291). And international law, if it is to be accessible, useful, and legitimate throughout the international community, needs to incorporate “non-Western—in the context of this book, Islamic—modes of legal thinking into international resolution venues” (p. 287). The thorough, accessible description and the careful conceptualization and empirical work of this book will be a valuable guide to such scholarship in the future and will no doubt stimulate future research that builds on the excellent model offered here.