In her masterful work, Is International Law International?, Anthea Roberts convincingly shatters our illusions about international law's universality, and makes the case for comparison in international law. Having already won the American Society of International Law's prestigious Certificate of Merit, the book needs no further praise. Instead, the real question is whether she will succeed in transforming the field, by persuading countless international lawyers focused primarily on our own domestic traditions to study other jurisdictions’ methods and doctrines. In this review, I argue that it would be a great loss if we did not take her up on this challenge, and explain why we must all dabble in comparative law.
Roberts's book is not a polemic—it is first and foremost a cartography. Indeed, it could be criticized as an exercise in description, even though it offers much more. Because Roberts is subtle, I get to be forceful, and to develop the full consequences for the field if we remain comfortable in our parochialism.
As we begin to explore uncharted territory, a few words on our guide. Roberts, now at the School of Regulation and Global Governance at the Australian National University, is unusually well-placed to map out the world of comparative international law. She has taught for years at prominent institutions in three countries, including at the London School of Economics and Columbia Law School. She has also served as arbitrator, counsel, and expert in international disputes.
Roberts starts by carefully mapping out distinct traditions in international law—and focusing on those of the permanent five UN Security Council members. This choice is a wise one: not only are these countries’ interpretations of international law particularly consequential, but their traditions reveal surprising differences. These differences, even among powerful states, go far beyond the traditional dichotomy separating the West from the rest. Through her mapping, Roberts persuades readers that the myth of a single international legal tradition is not just fraying at the edges, but is instead entirely unsustainable in an increasingly multipolar world.
Some first statistics regarding the study of international law assist in priming the reader for the size of the differences she uncovers. It turns out that when we are first taught international law, we are given very different materials to study (Figure 15, p. 167). For example, 70 percent of foreign judgments in Argentine casebooks are from the Spanish national courts, whereas over 80 percent of foreign cases in Cameroon or Senegal are from France. In contrast, it is U.S. cases that are most commonly taught to budding lawyers in the UK, but also in Japan, France, Germany, Brazil, and Russia. And the influence of the UK is even more pervasive—as UK cases are predominant not only in casebooks from former colonies, including the United States, Canada, South Africa, Australia, India, and Australia, but also in China.
In addition, the extent to which lawyers will be exposed to any foreign materials or ideas varies dramatically. For instance, whereas over 70 percent of academics in the UK have law degrees from multiple countries, the percentage falls to 40 percent for China, and to 30 percent for the United States. It falls below 10 percent for France and Russia (Table 3, p. 73). In sum, both the volume and type of training international lawyers receive varies greatly.
What difference does any of this make, however? Roberts suggests, tentatively but persuasively, that the consequences could be as far-reaching as the difference between isolation on the one hand and peace and prosperity on the other. She flags core moments of international tensions—including the Russian annexation of Crimea, the second Iraq War, and China's hostility to the South China Sea arbitration—to suggest they resulted only in part from diverging geopolitical interests. Implicit in her narrative is the principle that ideas matter. Isolated national academies and divergent intellectual traditions might have also contributed to the formation and slow resolution of these conflicts, and contributed to major foreign policy mistakes.
To illustrate, let me draw on the 2003 Iraq War. Roberts tracks how this conflict was covered in U.S., UK, and French textbooks. Whereas U.S. casebooks extensively debate the legality of the intervention, French textbooks give short treatment to the events, quickly concluding that the U.S. and UK intervention violated international law. Prominent UK textbooks give more extensive treatment to the justifications for the intervention, but again conclude that it was illegal (pp. 204–05). In contrast, it is U.S. casebooks alone that leave open the question of the 2003 Iraq intervention's legality. Indeed, they supply readers with extensive material supporting the intervention, and more limited materials in opposition (p. 205).
It is certainly worth wondering why U.S. casebook authors are still presenting very different viewpoints—even from their UK colleagues—on this highly problematic U.S.-UK intervention. We now have many reasons to revisit the wisdom of the 2003 intervention, including knowledge that Saddam Hussein lacked weapons of mass destruction, and knowledge that Iraq would descend into a brutal civil war. After all, hindsight is 20/20. But the critical question is whether American international lawyers, back in 2003, could have acted differently, and expressed more doubts about the legality of the intervention. The comparative analysis suggests that if American legal scholars had been more connected to their foreign counterparts, who were at the time and currently remain much more critical of the intervention, a different set of exchanges might have taken place.
But it is not only Americans who lose from the relative isolation of their legal academy. To see how isolation also harms the Chinese, let me briefly turn to the South China Sea arbitration. In this dispute, a United Nations Convention on the Law of the Sea tribunal adopted a broad ruling favorable to the Philippines and unfavorable to China. China objected to the arbitral tribunal's jurisdiction, and refused to participate in the proceedings. Privately, some scholars based in China believed that had China participated in the proceedings, if only to contest jurisdiction, this would have improved the chances it would prevail (p. 242). However, two factors prompted these scholars to stay silent. First, fear of censorship and soft retribution within the competitive Chinese academic market (p. 243). Second, genuine support for the Chinese government's position due to the scholars’ education, socialization, international law materials, and media sources (id.). However tentatively, this suggests that the relative isolation and parochialism has real costs for global policy.
Even if the above connections seem too tentative, failing to recognize the divergence of international law traditions has clear consequences for national academies. Here, there is a stark choice between irrelevance and global prominence. To cite one example: Roberts, updating Detlev Vagts, counts citations to the German Max Planck Encyclopedia of Public International Law (Encyclopedia) and to its French counterpart, the Juris-Classeur de Droit International (p. 100). By a couple of different metrics presented, the Encyclopedia is at least thirty times more influential. Undoubtedly, many factors contribute to the Encyclopedia’s success, but a bold choice for the German academy—publishing it in English—is certainly a prerequisite for the Encyclopedia’s global reach. This example sharply illustrates the cost of focusing inward, precisely because French, the traditional language of international courts and international law, is so widely used. Nevertheless, as Roberts and Vagts emphasize, even publishing in French—let alone in Russian or Chinese—severely limits global readership.
And, indeed, the advantages of cross-national connections do not accrue only to entire academies, but also to individual lawyers, at least in many jurisdictions. That said, professional incentives, as Roberts helpfully explains, differ dramatically depending on one's home jurisdiction. Comparative study is essential in the UK, exciting in China, welcome but far from central in the United States and France, and outright risky in Russia. Indeed, in Russia, in a fascinating inversion of the traditional hierarchy, in which “Western” is often assumed to mark relevance and quality, “Western” often connotes untrustworthiness (pp. 175–76).
That said, while Roberts focuses on the P-5, she also briefly includes data from less powerful states, in which comparative study is a clear marker of quality. Seen from the periphery, a foreign law degree is often a signal of prestige in one's home market (perhaps in addition to being functionally useful). This helps explain why top lawyers from around the world pursue LL.M. degrees in the United States, the UK, and France, when these markets remain hard to penetrate. That said, further study of the diffusion of laws and lawyers from the perspective of the periphery would be a very welcome addition to Roberts's analysis. While notable existing volumes exist, including my own The Democratic Foundations of Policy Diffusion,Footnote 1 and Arnulf Becker Lorca's Mestizo International Law,Footnote 2 there remains ample space for the comparative study of international law in many more jurisdictions.
International lawyers have long known that there are important reasons to dabble in comparative law. After all, to establish the meaning of international custom, or general principles of law, one must know whether a norm or practice is widely accepted around the world. I hope that the isolated examples presented above have added to these familiar arguments, and lead readers to see even greater merit in the study of comparative international law.
Before concluding, let me anticipate and try to briefly address the principle objection to the study of comparative international law. Becoming a comparativist would certainly be a good thing, ceteris paribus, international lawyers might argue. But this is a time-consuming and daunting task. International lawyers are certainly right to worry they might interpret foreign law incorrectly. And comparative law, as a field, has helped dig its own grave by insisting on an all-or-nothing proposition: Either one spends years studying a foreign legal system or one is lacking in the requisite credentials to speak authoritatively on it. Dabblers are not welcome.
Where does one even begin to dabble? Here, let me point to another of Roberts's efforts, in conjunction with Mila Versteeg, Paul Stephan, and Pierre Verdier. They have compiled both an American Journal of International Law Special Issue,Footnote 3 and an edited volume, Comparative International Law,Footnote 4 that contain extensive guidance, and many more examples, for the international lawyer who is curious, but does not quite know where to start.
And, as the goal is to simplify, rather than complicate the life of the potential dabbler, let me flag two particularly useful principles from the field of comparative law: functional equivalence and case selection. Functional equivalence is the idea that in studying a foreign system, one should not look for an identical rule, but rather for a rule that serves the same function. Case selection involves the principle that by carefully selecting country cases, one can make persuasive arguments with less data. The traditional approach of international lawyers to comparative study—the “brute force” approach—is highly inefficient. For example, an international lawyer trying to establish that certain weapons are prohibited by international custom would typically try to look far and wide, for as many treaty ratifications, declarations, military manuals, and other materials he could easily get his hands on, and then give up when he reached thirty or forty countries. That is not only exhausting, but also leaves him open to criticisms that many countries, and indeed entire categories of legal systems, are likely absent from his sample. In contrast, even a single strategically chosen observation might carry more weight. For instance, if even Nazi Germany, when facing the prospect of total defeat, refused to use particular weapons, this would greatly bolster the claim that this weapon was prohibited by international custom. I have written separately on sampling, most similar and most difficult case design, and other principles of case selection that comparativists have settled on.Footnote 5 But here, I am writing simply to emphasize that by strategizing carefully about what function particular rules play, and which cases to examine in depth, the dabbler will both follow best methodological practice and save precious time.
In sum, we need, as a field, to know whether particular positions are widely accepted around the world, or peculiar to our home traditions. International lawyers must become dabblers in comparative law. This is a hard, but worthwhile task, so shortcuts and collaborations are essential.
