Professor emeritus of international law at the University of Tokyo, ONUMA Yasuaki, has written a magnum opus that deserves the attention of anyone who is interested in challenging his or her perceptions of international law. Onuma emphasizes in the introduction to his book that ‘everything is to be doubted’ and ‘to doubt is a virtue’,Footnote ¹ referring to various European and Japanese thinkers of the past. Therefore, he will surely approve when I will also critically question certain aspects of his book – in fact, I would only follow his own advice when doing so!

By design, Onuma's book is a passionate and conceptual general course similar to the format of the course that he previously delivered at The Hague Academy of International Law. In many ways, the current book further develops the ideas and arguments of Onuma's lectures at the Hague AcademyFootnote ² and creates a comprehensive theory of international law.

The main idea is that international law should be examined through a transcivilizational perspective – and with this perspective in mind, Onuma walks the reader through central subject areas of international law, from the history and theory of international law to areas such as state responsibility, human rights, economic relations, environment, use of force, etc. A centrally important aspect is how Onuma understands the concept ‘transcivilizational’, the brand that he has coined in the field of international law. By ‘transcivilizational’ Onuma means that there is not just one human civilization (historically defined by Europe) but rather a plurality of civilizations and cultures which must be recognized as a starting point for contemporary international law. The prefix ‘trans-’, in turn means that legally important relations across the world and various civilizations do not develop just between the states (horizontally) but also include other participants in international law, such as non-state actors. Moreover, ‘civilizations’ in Onuma's concept are not rigid and monolithic but constantly changing and interacting.

Thus, Onuma distances himself from Samuel Huntington's idea of a clash of civilizations and warns against a too-essentialist understanding of civilizations: ‘Such a categorical differentiation and essentialization of civilization, culture and religion is simply wrong.’Footnote ³ For Onuma, globalization means that humans are mostly hybrids nowadays in the civilizational sense, as they are influenced by different civilizational legacies and impulses.

At the same time, as a general course on international law, Onuma's book is also unique and sometimes idiosyncratic. The book starts with a picture image by MAKIMURA Satoru of Grotius, Gandhi, Confucius and Marx showing the way of learning and enlightenment forward to a baby, accompanied by a message that ‘only with innocent eyes can one see the Light’. The book contains a number of strong opinions. In the preface, Onuma declares programmatically and critically:

Further in the book, the author opines: ‘The judiciary is not a major forum where international law is interpreted, disputed, used or abused, applied or realized. Fundamentally, dispute settlement is a pathology, not a physiology of law.’Footnote ⁵

In this sense, Onuma seems to follow the advice of Karl Marx: ‘The philosophers have only interpreted the world. The point, however, is to change it.’ (We can replace the word ‘philosophers’ in this quote with ‘positivist international lawyers’). In nineteenth century terms, although Onuma demonstrates an admirable knowledge of positive law throughout the book, he quickly outs himself as a natural law scholar who criticizes the existing legal relations and dogmas from the perspective of transcivilizational justice because he is quick to point out that not all existing international legal norms or practices are necessarily just from a transcivilizational perspective. Lex lata and lex ferenda constantly interact in this book but since Onuma believes that international law is a social construction, he clearly prefers to tell us how international law should evolve rather than just describing how it is typically seen in the doctrine. This is generally a plausible method but occasionally also takes the shape of advocacy in the context of international law.

Both in this book and in his earlier work, Onuma's primary strength as an academic writer is that he is first of all a critical historian of international law. His first major edited work in English, written together with other Japanese scholars, was published in 1993 and analyzed the work of Hugo Grotius.Footnote ⁶ This study, although produced outside the West, was altogether less critical of Grotius than some recent studies written in the West.Footnote ⁷ Studying the thought of Grotius and later, more generally, the historical evolution of international law in different regions of the world has decisively informed his criticism of Eurocentrism in international law. Onuma, the non-positivist, refers to the history of international law throughout his legal analysis. Critical historical analysis teaches him that in international law, over the last centuries and particularly over the last century, circumstances and doctrines have changed considerably. There is no reason why they could and should not change further and Onuma, the author, acts as agent and accelerator of the changes that he wants to see – by revealing the injustices of existing international law and suggesting ways for improvement.

Many historians of international relations end up being ‘realists’ (cf. Kissinger) and Onuma, too, sees his intellectual project as a realism of sorts.Footnote ⁸ In the preface, he explains that he seeks ‘to demonstrate the overall picture of international law actually functioning in international and domestic societies’.Footnote ⁹ Onuma's core argument is a profoundly political one: there has been and still continues to be an unjust and unjustifiable West-centric bias in the understanding and application of international law. Onuma suggests that ‘it is crucial to overcome excessive West-centrism and establish international law with transcivilizational legitimacy’.Footnote ¹⁰ However, the project of making international law truly universal is far from complete:

This is quite a curious and even radical argument because it raises the possibility that universal international law might not even exist, at least not yet, and that instead we have had some kind of historical European dictate presented as international law.

On a number of occasions, Onuma takes an external perspective on international law and challenges what he sees as predominant truths in the field. For example, he thinks that the role of international adjudication has been over-emphasized by academics at the cost of non-judiciary, including diplomatic, expressions of inter-national law:

Very interesting and quite radical is his discussion of the sources of international law. For example, Onuma fundamentally criticizes the concept of custom in international law: ‘International lawyers should liberate themselves from a longstanding reliance on Article 38 and “customary” international law, which is basically a misnomer.’Footnote ¹³ Onuma's main criticism is that general international law is wrongly equated with customary international law in the doctrine.Footnote ¹⁴ However, most of the traditional ‘customary’ norms were formulated by Western international lawyers during the colonial period.Footnote ¹⁵ Such rules cannot lay any claim to true universal binding-ness. I think there is certainly a grain of truth in this claim – for example, I have often wondered how self-evidently some Anglo-Saxon writers consider the 1837 Caroline case (which was a case between the US and Britain) formulating criteria for preemptive self-defence as indicative of customary international law more generally.Footnote ¹⁶ Yet it is not certain that, for example, countries like Russia (or the USSR) ever considered these criteria binding as customary international law.

Furthermore, Onuma thinks that to reduce the sources of international law to the list in Article 38 of the ICJ Statute is far too narrow: ‘Some resolutions adopted by the UN GA are far more legitimate and important and have actually been more often used than, for example, the “general principles of law recognized by civilized nations” provided in Art 38.’Footnote ¹⁷ Altogether, Onuma is very critical of the ways in which the sources of international law have so far been theorized; his project is to open up and diversify these sources. For example, resolutions adopted by the UN General Assembly as well as at politically important conferences (such as the Helsinki conference of 1975 or Vienna conference of 1993), may constitute a ‘cognitive basis for identifying general international law’.Footnote ¹⁸

Moreover, Onuma suggests abandoning the discriminatory concept of ‘subjects of international law’ (since it historically favours states, or rather their governments) and use the more inclusive concept of ‘participants’ in international law instead.Footnote ¹⁹ Beside states and their governments, he includes individuals, NGOs and generally non-state actors among the participants in international law. In my reading, he dedicates somewhat less intellectual energy to empowering transnational corporations as participants in international law – probably because their power has already been considered as suspicious both by third world and Soviet approaches. Nevertheless, the end result is the opening up of international law ‘progressive’ (non-state) actors.

Furthermore, Onuma is not convinced by the usual definition of states in international law (i.e., the 1933 Montevideo Convention)Footnote ²⁰ because it is based on a formalistic nineteenth century theory and does not fully take into account contemporary developments in contexts such as illegal annexation or apartheid. Moreover, Onuma thinks that the two classical theories of the recognition of statehood are quite useless.Footnote ²¹ He is not at all sure that the ILC Articles on State Responsibility of 2001 manage to effectively regulate state responsibility in matters of high politics such as use of force or genocideFootnote ²² because they rather resemble a beautiful theory or an ideal standard that may not work in practice when the stakes are particularly high for predominant states. In this sense, Onuma really doubts all aspects of the predominant discourse of international law.

Onuma tells us where the power lies in the context of international law and that it is often distributed unjustly. He criticizes the fact that in the ICJ, judges elected from Europe and North America still compose almost half of the bench, numbering seven out of 15 judges.Footnote ²³ Moreover, given that the Chinese and Japanese judges have occupied two of the three Asian seats, representatives of Islam and Hinduism have, for a long time, been effectively excluded from serving on the ICJ bench.Footnote ²⁴ He argues that permanent members of the UN Security Council should not automatically expect a seat to be reserved for one of their nationals. Quite fittingly, the ICJ elections of November 2017, when the UN General Assembly favoured an Indian candidate over a British one, demonstrated that Onuma's concern was widely shared among non-Western states.

While emphasizing the realist roots of his intellectual project in the beginning of his treatise,Footnote ²⁵ Onuma is occasionally quite idealistic about diverse ‘progressive’ forces beyond the state. For example, he writes in the context of responses to violations of international law:

However, are these actors really capable of efficiently preventing and correcting illegal acts of states, for example illegal uses of force? While praising NGOs and other newer participants in international law, Onuma at the same time questions their limited accountability and sometimes Western-centric arrogance – when, for example they are occasionally ‘insensitive to the negative consequences of their activities’Footnote ²⁷ or ignore ‘the multifaceted aspects of a problem, and its cultural, religious, and historical subtleties’.Footnote ²⁸

For me personally, one of the most interesting chapters was the one on human rights from a transcivilizational perspective. In the introduction to the chapter, Onuma challenges Western perceptions by citing a twentieth century Japanese novelist, TAKAHASHI Kazumi:

Of course, we can guess that, from the Buddhist point of view, Westerners with their often materialistic ‘pursuit of happiness’ might be ‘enslaved to their desires’ (in Protestantism acquiring material wealth was proof that one was ‘chosen’ and loved by God). Thus, they are as far from ‘heaven’ as poorer peoples often living under non-democratic regimes that violate human rights (‘weeping from misfortune’). Onuma values the Vienna Declaration of 1993 very highly from an intercivilizational perspective – mostly because, unlike in 1948, all states participated in working out the relevant formulations. At the same time, Onuma regrets that, while being a useful compromise on the issue of universality of human rights,Footnote ³⁰ the Vienna Declaration has subsequently been underappreciated.Footnote ³¹ When discussing human rights, Onuma reveals his syncretistic approach, trying to accommodate different positions that for others may seem irreconcilable. For example, he thinks that international law should promote universal human rights but also has some understanding for views that go against the Western predominant concept of human rights, like the 1990 Cairo Declaration on Human Rights in Islam: ‘Still, the need to hear these “different”, non-prevalent voices should be emphasized.’Footnote ³² In this way, Onuma calls us to understand the history of many non-Western societies in the context of human rights, as their path from collectivist and religious identities to the normative claims based on human rights has not been an easy one: ‘In societies where Islam, Confucianism, Hinduism and Buddhism have been prevalent, people have been urged to change their identity, the critical sense of the self, in accordance with rapid globalization, including human-rightization of the society.’Footnote ³³ Non-Western societies may, then, just need more time to make individualist concepts of human rights truly their own.

Although Onuma favours the functional rather than essentialist concept of ‘civilizations’, he is himself relatively persistent in dividing the world into the West (or Europe, its international legal legacy, and outlier states) and the non-West in international law.Footnote ³⁴ However, the wider West is not as monolithic as Onuma seems to suggest, probably for simplicity's sake. For example, small states in Europe have often painful experiences with ‘European’ international law, different from the historical Great Powers in Europe. If we understand the wider West (or Christian Europe; the former stakeholders in jus publicum europaeum) as including Russia and Russian-influenced parts of Central Asia, then there is much more diversity and conflict in the ‘intra-Western’ discourse of international law than Onuma's grand canvas postulates.

To sum up the narrative in this review, Onuma's work is a thorough criticism of the Western predominance in the field of international law. Its main message is that power should be shared much more equally in various contexts of international law. Of course, if our understanding of international law is mainly a reflection of material and ideational power as Onuma seems to claim, then interpretations of international law will inevitably change as global power shifts from the West to Asia. However, material and ideational power do not necessarily go hand in hand; there is no automatism in the shift of ideational power. Onuma's treatise can also be perceived as self-criticism of Asian cultures, stating that their existing and growing material and military power does not correspond to an equal increase in ideational power in international law, including its scholarship, and this may not only be the West's fault, at least not any more.

Onuma characterizes Western culture as ‘legalistic’, but perhaps it was also this ‘legalism’ that helped to produce international law as we know it. When the West loses power, ‘international law’ may become less important in the world order – if non-Western powers see it as ‘a foreign language’ and prefer to make normative claims in another way or language. As of today, it is not always clear whether China, for example, would want to build the future world order, especially the South East Asian regional order, predominantly on ‘international law’ in the way that Western powers created it (avoiding hegemon–vassal relationships that were characteristic to the Sinocentric order that existed before the arrival of Europeans).

However, one does not need to agree with all the answers that Professor Onuma provides. Reading this book, I very much appreciated the questions raised and that Onuma did not shy away from controversies in his analysis, for any possible tactical reasons any international lawyer might have. I take my hat off to the erudition, courage, and personality that Onuma demonstrates in this book that I predict will become a major reference work in the field of international law in the twenty-first century.