Symposium on Rewriting Histories of the Use of Force: The Natural Law Past and Future of the Prohibition on the Use of Force

[Mary Ellen O’Connell is the Robert and Marion Short Professor of Law and Professor of International Peace Studies, University of Notre Dame. O’Connell’s research is in the areas of international law on the use of force and international legal theory.]

Agatha Verdebout’s Rewriting Histories of the Use of Force belongs with Philip Allott’s Health of Nations, Martti Koskenniemi’s Gentle Civilizer of Nations, and Stephen Neff’s Justice Among Nations. All are incisive works of legal and intellectual history explaining the emergence of certain pivotal concepts that continue to shape international law today. This knowledge opens the mind to possibilities for law reform—reform, for example, of the law on the use of force, the focus of Rewriting Histories. Verdebout investigates why 20^th and 21^st century scholars came to consistently misrepresent the 19^th century position on the prohibition. The error has likely contributed to the prohibition’s current weak pull to compliance seen, most recently, in the failure to prevent Russia’s war against Ukraine, devastating internal armed conflicts, egregious situations of long-term occupation, and targeted killings.

Rewriting Histories is presented as a high-stakes mystery—which it is—where the author solves the case, discussing her sophisticated methodologies in an accessible fashion along the way. The mystery is that, with very few exceptions, international law scholars have repeated since World War I that resort to war by sovereign states was not prohibited under international law until the first decades of the 20^th century. International law was simply silent or “indifferent” to a sovereign state’s prerogative to resort to war. At the same time, most of these scholars also contend that armed force short of war was clearly regulated in the 19^th century. Think only of the Caroline correspondence. Any evidence to the contrary is typically dismissed as mere natural law moralism as opposed to proof of “real law”, which means positive law.

Verdebout sweeps away the dismissals with a meticulous presentation of empirical evidence. She shows that 19^th century international law scholars did not hold the self-evidently contradictory position that measures short of war were outlawed while war itself was not. She draws on over 80 textbooks published between 1815 and 1914 to prove her case. She provides plenty of context, nuance, and caveats to show that the weight of the evidence decisively counters the “indifference” narrative—neither states nor scholars believed international law was “indifferent” to the legality of sovereign states resorting to war. Perhaps of greatest significance, she finds that the members of all three primary theoretical schools of the period, which she names “Naturalist”, “Eclectic”, and “Positivist”, held that international law regulated war as much as any measure short of war.

The fact the Positivists believed this, too, may come as the biggest surprise, but the evidence tracks my own findings. I describe the three categories of 19^th century international legal theory somewhat differently than Verdebout. The category she calls “Eclectic” is not so much eclectic as the classical natural law theory that integrates natural and positive law. For present purposes, it is enough to underscore that Verdebout is willing to take up a discussion of natural law, as are increasing numbers of international lawyers. It is a topic essential to understanding the past and future of legal theory.

With her case made respecting the three schools, Verdebout turns to the more challenging aspect of the mystery: Why would so many prominent scholars refuse to believe the same evidence she was able to find for so long? Her answer is compelling and resonant. She shows that scholars needed to believe international law was not to blame for the senseless death and destruction of World War I.  If no prohibition on force existed, no fault could be laid at the door of international law. The blame belonged entirely to politicians and political theories like raison d’etat.  In the aftermath of the disaster, the lawyers were needed to step in with law and institutions to ensure future peace beginning with the League Covenant, the League itself, and the Permanent Court of International Justice.

If, however, scholars acknowledged that a prohibition on war existed, then the law had failed catastrophically. International law was not, in fact, the tool for good as promoted by its advocates. Verdebout uses linguistic analysis to show that lawyers indeed saw the purpose of law to be the creation of harmonious order—the peace necessary for the flourishing of humanity. To handle the cognitive dissonance between this understanding of law’s purpose and its evident, extensive failure in 1914, Verdebout uses social psychology to explain how myths are made. In this case, she shows how a myth about the absence of law helped international lawyers deal with facts that defied their beliefs.

Cognitive dissonance after World War I, however, does not fully explain why the myth persists more than a century later. On this issue, more insights from the analysis of international legal theory can support Verdebout’s case. She acknowledges that a few scholars rejected the myth from the start, including Kelsen and Stisower. A small group of contemporary scholars continue to reject it, including Corten, Tourmé-Jouannet, Lesaffer, and myself. Understanding why some resisted may uncover why most others have not. Verdebout says that in my case, I only raise the fact that international law did prohibit resort to force in the 19^th century but fail to “interrogate” why a contrary view dominates the literature.

She is correct that I say little on the topic in the Oxford Handbook of the History of International Law, which she cites. But in other publications there are some answers. I accept Verdebout’s analysis about the role of cognitive dissonance in creating the myth of indifference, but additional factors were also at work. The theory of natural law that accounts for the existence of the prohibition on the use of force in international law came under attack throughout the same period Verdebout studies. She finds three schools in existence in the 19^th century, but by the end of World War I, most international lawyers were only acknowledging positivism. Positivists might be forgiven for concluding no law existed against the use of force in the 19^th century. There were no treaties, for example. The positive law Verdebout reports on is customary international law and that is easily dismissed in the age positivism as mere natural law of no consequence. Further, some of the 19^th century positivists Verdebout reports on were still influenced by natural law. There was no pure theory of positivism. Triepel, Jhering and others were trying to get there, but could not succeed until international institutions came into existence to obscure the theoretical deficits of positivism.

If law existed to prohibit World War I, then the law did indeed fail—both the positive and natural law prohibitions. With Verdebout’s book, the myth can no longer serve to obscure this truth. Verdebout says little about the implications of exploding the myth. She has, however, added to my own understanding of how the ancient natural law prohibition on the use of force could become so completely forgotten by the mid-20^th century. The suppression of natural law had already begun with the rise of the state system and the end of central authorities to oversee the law, in particular the prohibition of force. More pressure against natural law came with the rise of science and the emphasis on material proof that favored positive law theory over natural law. Positive law also suited European governments and the U.S. It freed them from the natural law principle that law is superior to sovereign states, as well as principles of universality, equality, and peace. In their place Europeans and Americans promoted positive law concepts of absolute sovereignty and civilizational hierarchy. As is well documented, both concepts were used in justifying military, economic, and cultural domination abroad. These states could argue that positive law permitted “civilized” states to exercise dominion over inferiors, an argument anathema in natural law. The attraction of positivism was strong enough for many scholars to believe natural law had been replaced by the end of the 19^th century despite the considerable theoretical gaps left in the law.

Rewriting Histories confirms what I present in a forthcoming chapter of the Oxford Handbook of International Law in Europe. Theorists turned to international institutions to fill the gaps left by the suppression of natural law. This move seemed to work respecting national law. Government institutions have legal authority through the myth of a social contract; people give their hypothetical consent to be bound by government authority and positive law. With the creation of global organizations like the League of Nations, a parallel myth of the social contract could be posited. The problem is that the explanation of why consent binds—hypothetical or real—is not found in positive law theory. It is found in natural law theory. Natural law also explains that some law is invalid even with consent, law that would legalize the use of force in conflict with the prohibition, for example. Nevertheless, World War I motivated the creation of institutions and the adoption of positive law, as Verdebout shows. The Covenant, the UN Charter, and the jurisprudence of international courts could be seen as substitutes for the positive law institutions of national governments. Consent to all these positive-law developments has served to distract from the need to explain why consent to social contracts or treaties can bind in the first place. As Anthony Carty argues so persuasively, positive law in whatever form cannot fully replace natural law. Even the great Positivist H.L.A. Hart acknowledged in the middle of the 20^th century that some natural law theory is necessary for a complete theory of law and the institutions formed under law.

Without natural law, the post-World War I institutions could only accomplish so much. Little wonder one attempt after another has been made to improve them and the positive law against war. The Kellogg-Briand Pact improved on the League Covenant. The effort was repeated with the United Nations and the Charter. Without natural law, however, the notion took hold that the prohibition on force could be changed like any other rule of positive law with changing state practice and declarations of opinio juris. Consider the attempt to justify the use of force by claiming that a state “unable or unwilling” to comply with another state’s will, may be attacked. The assertion speaks volumes about the fading knowledge of natural law. Hersch Lauterpacht delivered his cri de coeur in “The Grotian Tradition” in 1946 so that international lawyers would again honor natural law when the post-World War I positive law and institutions failed to prevent World War II. Yet, by the end of the Cold War, the emphasis on positive law and institutions only continued with the development of international criminal courts.

Law needs institutions. It needs the positive law, but it also needs enduring natural law norms, and a robust explanation of why human beings are bound by certain principles regardless of consent. Even with all these elements in place, the law will be challenged by violators. The best chance of responding successfully is to accurately assess the historical record and its lessons about the nature of law. Law existed against war in the 19^th century. It was still influenced by natural law theory but the pull to compliance was being weakened through preference for positive law alone. Positive law scholars of the post-World War I period chose to see no law at all in the 19^th century, rather than acknowledge the existence of the prohibition on force and how it had been undermined by rejecting natural law. Verdebout’s book will inspire rigorous new scholarship committed to understanding and strengthening not only the authentic prohibition on the use of force but all international law.