Victor's Justice: Unpacking the Tokyo War Crimes Tribunall

by Christian Rowbotham

Part 4: Ex Post Facto Laws

Examining the provisions invoked and applied during the trial is essential to assessing the legitimacy of the International Military Tribunal for the Far East (IMTFE). Legal scholar Neil Boister, among others, cites U.S. Supreme Court Justice William O. Douglas's perspective that the IMTFE was shaped more by political motives than by a fair application of existing international law.
Article 5 of the IMTFE Charter defined the tribunal's jurisdiction over three categories of offenses:

• Class A: crimes against peace (planning, preparation, initiation, or waging aggressive war, or participation in a conspiracy to do so);
  
• Class B: conventional war crimes;
  
• Class C: crimes against humanity.
  

Conventional war crimes (Class B) rested on well-established violations of the laws and customs of war, as codified in prewar conventions like the Hague Conventions. In contrast, crimes against peace (Class A) and crimes against humanity (Class C) were far more controversial. Lacking clear, universally accepted legal precedent at the time, these charges were often criticized as ex post facto (retroactive) and politically motivated, designed to legitimize the prosecution of Japanese (and earlier German) leaders.
Unlike the Nuremberg Charter (for the IMT), the IMTFE Charter made crimes against peace the central focus of the indictment. The tribunal treated this offense as the "supreme international crime," containing within itself the accumulated evils of war. All defendants had to be charged under this category as a prerequisite for the tribunal's jurisdiction over the other offenses.
According to the American delegation's proposed definition at the London Conference of 1945 (which influenced both the Nuremberg and Tokyo charters), a war of aggression was characterized by a state being the first to undertake hostile actions against another, including:

• declaring war;
  
• invading its territory with armed forces (with or without declaration of war);
  
• attacking its land, naval, or air forces, territory, vessels, or aircraft;
  
• imposing a naval blockade; or
  
• supporting armed bands that invade another state, or failing to prevent such bands from receiving support within its territory.
  

No political, military, economic, or other considerations could justify such actions, though legitimate self-defense or aid to a victim of aggression was exempted.
Under the IMTFE Charter, the indictment embodied the Allied perspective that Japanese "aggressors" bore sole responsibility for the Pacific War. The prosecution alleged that the accused had participated in the "formulation of… a common plan or conspiracy" to achieve domination of the Far East through armed force and, in alliance with the Axis powers, eventual domination of the world. This allegation underpinned the core charge of crimes against peace (Count 1 of the indictment).
Historian Richard H. Minear, in Victors' Justice: The Tokyo War Crimes Trial, observes that the tribunal adapted historical and political circumstances from the German case at Nuremberg to fit Japan, thereby justifying the application of the broad "conspiracy" charge despite significant differences in the two nations' contexts and leadership structures.
For the United States, the Japanese leadership was deemed to have waged an unlawful war of aggression, beginning with the attack on Pearl Harbor on December 7, 1941. The majority judgment held Japan liable for crimes against peace against both the United States and the United Kingdom. It found that, following prolonged but ultimately futile negotiations with the U.S. government, Japanese leaders conspired to initiate a war of aggression against the United States and the British Commonwealth. Eighteen of the twenty-five convicted defendants were found guilty on this count.
The majority also addressed the surprise nature of the Pearl Harbor attack in relation to Hague Convention III of 1907 (Relative to the Opening of Hostilities), which required that hostilities not commence without previous and explicit warning—either a reasoned declaration of war or an ultimatum with conditional declaration. The convention did not specify a minimum notice period. Evidence showed that Japanese planners intended to deliver only about twenty minutes' notice before the assault, which might have technically satisfied the narrowest interpretation of the rule. However, due to transmission delays, the formal notification reached U.S. officials after the attack had begun, rendering it a surprise assault in violation of international law and reinforcing the aggressive character of the war.

(Notably, Prince Fumimaro Konoe, who served as Prime Minister during much of the critical pre-war negotiations with the United States and was initially considered for indictment as a Class A suspect, committed suicide on December 16, 1945, shortly after Japan's surrender and before formal charges were filed, by taking poison rather than face potential trial.)
The tribunal therefore convicted the defendants of aggression against the United States not primarily because of the manner in which the Pacific War began, but because Japan's initiation and waging of that war—exemplified by the Pearl Harbor attack—constituted a war of aggression in violation of international law. The Allies viewed it as aggression because Japan, as a signatory to the Kellogg-Briand Pact of 1928 (Pact of Paris), had renounced war as an instrument of national policy. Article I of the Pact explicitly condemned recourse to war for the resolution of international disputes and renounced it in relations among the signatories. The majority judgment held that Japan's leaders knowingly violated this binding commitment by planning and launching aggressive wars, rendering such actions criminal under the evolving principles of international law recognized at the time.
Alongside the Nuremberg Tribunal, the IMTFE is now regarded as a foundational development in international criminal justice. It established the principle of individual criminal responsibility for core international crimes—crimes against peace, war crimes, and crimes against humanity—setting precedents that influenced the later creation of the International Criminal Tribunal for the former Yugoslavia (ICTY) and the International Criminal Tribunal for Rwanda (ICTR).
The Potsdam Declaration (1945) underscored that the Allies sought "stern justice" against war criminals but did not aim to punish the Japanese people as a whole. Rather, it targeted those responsible for aggression and atrocities. Accordingly, the tribunal imposed individual liability on Japanese officials for crimes against peace primarily because the defendants knew or should have known that waging aggressive war contravened international obligations, including those under the Kellogg-Briand Pact. As a signatory, Japan was bound by the Pact's provisions, which the prosecution successfully argued criminalized aggressive war, holding the accused personally accountable for their roles in its planning, initiation, and conduct.
The IMTFE rejected the defense that wars of aggression were mere "acts of state" incurring no individual criminal responsibility. Instead, the majority judgment affirmed that "international law imposes duties and liabilities upon individuals as well as upon states." Citing the U.S. Supreme Court's decision in Ex parte Quirin (1942), the tribunal emphasized that "crimes against international law are committed by men, not by abstract entities, and only by punishing individuals who commit such crimes can the provisions of international law be enforced."
Article 5 of the IMTFE Charter granted the tribunal authority to try and punish Far Eastern war criminals—whether as individuals or as members of organizations—for offenses including crimes against peace, conventional war crimes, and crimes against humanity. Article 6 explicitly provided that neither an accused's official position nor obedience to orders from their government or superior would, in itself, absolve them of responsibility for such crimes, though these factors could mitigate punishment if justice required.
The majority held that a state acts only through individuals, who must bear personal responsibility for the state's aggressive actions or for failing to prevent them. While states have traditionally been held accountable for launching aggressive wars through mechanisms like reparations to injured parties, the tribunal deemed this approach outdated in the postwar era. Instead, it prioritized individual accountability for those—particularly militarists and leaders—who planned, initiated, or waged such wars.
In stark contrast, Justice Radhabinod Pal dissented vigorously on this point. He rejected the derivation of individual criminal responsibility from the collective acts of a state, arguing that general international law traditionally excluded liability for officials acting in their official capacity as government representatives. Pal acknowledged potential exceptions but insisted they required clear rules of customary international law or binding treaties, neither of which existed before the World Wars. Consequently, he contended that victorious powers could not retroactively criminalize such acts through ex post facto legislation that punished conduct not deemed criminal at the time it occurred. Pal highlighted what he viewed as double standards and colonial hypocrisies among the Allied powers, noting that interwar recommendations from unofficial bodies for individual accountability had not been formalized into binding law, a deliberate omission, in his view. Only after World War II, he argued, did the Allies selectively impose individual responsibility.
However, Chinese IMTFE Judge Mei Ju-ao countered such criticisms by arguing that precedents for individual criminal responsibility under international law already existed well before the postwar tribunals. For instance, piracy and human trafficking have long been recognized as international crimes, prosecutable by any state regardless of nationality or territoriality. Similarly, war crimes are fundamentally individual violations of international law, and their trial and punishment cannot be confined to the framework of domestic criminal law. In international courts, international law is applied directly, whereas in domestic courts it is incorporated into the national legal system through generalization or enumeration. Ultimately, Mei Ju-ao maintained, the legal foundation for punishing war criminals rests on established sources such as the Hague Conventions and the recognized laws and customs of war, which form indisputable parts of international law.
The central controversy surrounding the charge of "wars of aggression" (crimes against peace) lies in the absence, prior to Nuremberg and Tokyo, of a universally accepted definition of aggression grounded in general state practice and opinio juris. Likewise, "conspiracy" to commit aggression was not clearly established as a standalone crime under international law at the time; critics, including Justice Pal, argued that its application constituted ex post facto law, punishing conduct that was not criminal when committed. Efforts to codify a definition of aggression culminated only on December 14, 1974, when the United Nations General Assembly adopted Resolution 3314 (XXIX). Its Article 5 states: "No consideration of whatever nature, whether political, economic, military or otherwise, may serve as a justification for aggression." This resolution, while influential, is non-binding and has been criticized as ineffective in resolving ambiguities around the term "war of aggression." Even today, the "crime of aggression" remains subject to interpretive challenges under the Rome Statute of the International Criminal Court (1998, with the relevant amendment adopted in 2010 and activated in 2018), as noted by scholars such as Maria Hsia Chang and others analyzing its limitations.
Justice Radhabinod Pal dissented most forcefully from the majority, standing alone in rejecting the criminalization of aggressive war under pre-existing international law. He argued that the Kellogg-Briand Pact of 1928 was merely a renunciation of war as an instrument of national policy, without criminalizing aggression or establishing individual responsibility. Pal famously remarked that "only a lost war is a crime," underscoring his view that the legality of war depended on its outcome rather than objective standards. He further contended that Japan could legitimately invoke self-defense under the Pact—a sovereign right he deemed inherent and not limited "by implication." In Pal's opinion, the Pact left the legal status of war unaltered, as the determination of whether a war was defensive remained a political decision for each state, not a justiciable legal question.
Scholars such as Maria Hsia Chang and Robert Parker have highlighted how the absence of a clear, universally accepted definition of "wars of aggression" was exacerbated by uncertainty in distinguishing them from legitimate self-defense. Critics of the Tokyo Tribunal point out that, until at least 1944, major powers including the United States, Great Britain, and France maintained that aggressive war was not yet a crime under international law, precisely because self-defensive wars could not be prohibited. Justice B. V. A. Röling (Netherlands), in his partial dissent, similarly argued that violence in self-defense, including responses to non-military threats, was still widely accepted, and the Kellogg-Briand Pact permitted each state to unilaterally determine what constituted self-defense and when the right could be exercised.
Even assuming the Pact outlawed aggressive wars (a premise Pal rejected), debate persisted over whether individuals could be held criminally accountable for state acts. Professor Knut Ipsen of Ruhr University echoed aspects of Pal's reasoning: while disagreeing with Pal that Japan's resort to war was legal, Ipsen concurred that the Pact's renunciation obligation bound states, not individuals. He thus questioned the tribunal's jurisdiction over crimes against peace, deeming it doubtful.
Justice Henri Bernard (France) concurred with the majority that aggressive war constituted an international crime for which individuals could bear criminal responsibility, but he reached this conclusion on distinct grounds. Rather than relying on the IMTFE Charter or the Kellogg-Briand Pact, Bernard invoked the European tradition of natural law—a higher, universal standard of justice rooted in reason and conscience, eternal and independent of positive law or tribunals. He viewed aggressive war as "always... a crime in the eyes of reason and universal conscience."
Bernard's dissent thus rested on philosophical foundations: legitimacy derived from immutable moral principles rather than statutory enactments like the Charter. This approach paralleled postwar natural law arguments by scholars such as Gustav Radbruch, who, drawing on similar traditions, asserted that grossly unjust laws (e.g., Nazi legislation) were not true law and could be disregarded.

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