The Birth and Evolution of International Criminal Law

by JK

Introduction

Born from the ashes of World War Two (“WW2”) in Nuremberg and Tokyo, International criminal law (“ICL”) is the body of law that holds individuals accountable for humanity’s most serious crimes. Too often reduced to headlines about geopolitics, tyrants, and war criminals, ICL is a landmark system that marked a turning point in the pursuit of universal justice by declaring some crimes so serious that they concern all of humanity and demand international cooperation. Positioned at the crossroads between international law, which governs relations between states, and domestic criminal law, which punishes individuals, ICL represents the idea that no leader or soldier is above the law. This blog, the first in a three-part series examining ICL alongside case studies on Myanmar and Ukraine, will trace ICL’s development from the Nuremberg and Tokyo Tribunals, through the Cold War, to the Rome Statute and the establishment of the International Criminal Court (“ICC”).

The Birth of ICL: the Nuremberg and Tokyo Tribunals

Following their victory in WW2, the Allied powers established International Military Tribunals (“IMT”) in Nuremberg and Tokyo to try war criminals from the German and Japanese forces.[i] While quasi-judicial commissions were established in the past to investigate breaches of the laws of war, it was not until Nuremberg and Tokyo that prosecution took place before an international forum and on the basis of international law.[ii] These IMT’s were without precedent as nations with vastly different governments and legal traditions united to bring a defeated enemy before a court of law. Rather than relying on arbitrary vengeance so often characterized by the term “victor’s justice,” a different route was taken. The Allies pursued a trial grounded in legal process and the rule of law. It marked the first moment in history when individuals themselves, not just states, were held criminally responsible under international law.[iii]

The Nuremberg IMT was formally established by the London Agreement on August 8, 1945, between the UK, US, France, and USSR.[iv] A foundational document for ICL, the agreement and its accompanying charter established the principle of individual responsibility under international law and defined the core offences of ICL: (a) crimes against peace, (b) war crimes, and (c) crimes against humanity.[v] These categories, and the Tribunal’s judgement over individuals such as Karl Dönitz (Commander of Germany’s U-Boat fleet), Wilhelm Frick (Reich Minister of Interior), Hans Fritzsche (Head of the Radio Division of the Propaganda Ministry), and more shaped later institutions such as the tribunals for the former Yugoslavia and Rwanda, and ultimately the ICC.[vi] In the end, both tribunals concluded with modest results: the Nuremberg IMT convicted nineteen defendants, sentencing twelve to death and the remainder to prison terms, while declaring the criminal character of four organizations.[vii] In Tokyo, all but three of the twenty-five accused were found guilty; two died before the proceedings concluded, and one was acquitted.[viii]

While groundbreaking, the Nuremberg and Tokyo Tribunals were not without controversy. Many contemporaries accused them of practicing “victor’s justice,” arguing that the trials punished only the defeated while overlooking crimes committed by the victors.[ix] Others questioned their legality, reasoning that some charges, such as “crimes against peace”, had no clear basis in existing international law at the time and were thus applied retroactively.[x] The tribunals also lacked universal representation as its judges came solely from the Allied powers, and no Axis officials were among the prosecutors.[xi] August von Knieriem, a German jurist, claimed that it was “incontestable” that “[t]he Nuremberg Tribunals were not international but American tribunals.”[xii] These concerns instigated an uneasy tension between morality and legality at ICL’s inception, and prompted later institutions such as the ICC to address these concerns, such as multi-national judges. Yet, the enduring criticism that ICL is shaped by political power rather than pure legality continues to shadow the field today.

The Cold War

In its first session on December 11, 1946, the General Assembly of the United Nations unanimously adopted a resolution confirming “the principles of international law acknowledged in the Charter of the Nuremberg Tribunal and in the judgment of this Tribunal.”[xiii] While the foundation of ICL was thereafter established, its development was about to take a turn for the worse. From Stettin in the Baltic to Trieste in the Adriatic, “an iron curtain…descended across the [European] Continent.”[xiv]

After a period of impressive achievements with the Nuremberg Charter and IMT’s, the field of ICL entered into a dormant state during the Cold War. In the dual-polar world that characterized the back half of the 20^th century, many countries stood divided between East and West. Lack of international cooperation was a predictable result, and the development of ICL took a long hiatus. Only after the fall of the Soviet Union did the wheels begin turning again. The first test: the ad hoc tribunals for Yugoslavia and Rwanda in the early 1990s.

International Criminal Tribunal for the former Yugoslavia

Due to the ongoing raging ethnic conflict in the former Yugoslavia, the UN Security Council (“UNSC”) adopted Resolution 827 on May 25, 1993, that formally established the International Criminal Tribunal for the former Yugoslavia (“ICTY”).[xv] This was a monumental breakthrough for the development of ICL as the five members of the UNSC, now more easily able to reach consensus than in the past, was able to step in and take concerted action over a situation threatening international peace and stability. The ICTY was given jurisdiction over four crimes: (1) genocide, (2) crimes against humanity, (3) violations of the laws or customs of war, and (4) grave breaches of the Geneva Conventions.[xvi] The ICTY was the first international criminal tribunal since Nuremberg and Tokyo, and it often had to create systems and rules from scratch, leading to considerable scrutiny.[xvii] For many, the ICTY was seen as a test for the credibility of not only international law, but of the international community’s ability to confront atrocities. While it continued to face obstacles such as the concealment of fugitives or evidence by certain states, by 1997, the ICTY had demonstrated to the world that ICL was not abstract theory but an enforceable system of accountability.[xviii] In the end, the ICTY indicted 161 individuals, sentenced 90, acquitted 19, and gave 13 referrals to national courts.[xix] As of July 2011, no fugitive remained.[xx]

International Criminal Tribunal for Rwanda

In 1994, a year after the establishment of the ICTY, reports of atrocities on an unimaginable scale were reported in Rwanda as extremist members of the Hutu majority were carrying out a coordinated genocide against the Tutsi minority.[xxi] With an estimated death toll of 500,000 to 1,000,000, in the same manner that it had with the Yugoslav conflicts, the UNSC deemed the situation in Rwanda as a threat to international peace and stability and thus established the International Criminal Tribunal for Rwanda (“ICTR”).[xxii] 

On September 2, 1998, the Trial Chamber of the ICTR found former teacher and politician Jean-Paul Akayesu guilty of genocide.[xxiii] This case was a significant milestone as it distinguished the ICTR as the first international tribunal to enter a judgement for genocide and the first to interpret the definition of genocide set forth in the 1948 Convention on the Prevention and Punishment of the Crime of Genocide.[xxiv] Moreover, the Trial Chamber discussed at length how rape and sexual violence constituted “serious bodily or mental harm”[xxv] inflicted with genocidal intent. This marked the first time an international court recognized rape and sexual violence as constitutive acts of genocide and crimes against humanity.[xxvi] After more than 20 years of operating, the ICTR rendered its final judgement and ceased operations in December 2015.[xxvii] In all, the ICTR indicted 93 individuals, resulting in 61 convictions, 14 acquittals, and five referrals.[xxviii] As of June 2024, no indicted individuals remained at large.[xxix]

The Rome Statute and the ICC

On July 17, 1998, 160 States gathered to adopt the Rome Statute of the International Criminal Court (“the Rome Statute”).[xxx] For the first time in human history, independent and sovereign states agreed to accept the jurisdiction of a permanent ICC for the prosecution of criminals who commit the most serious crimes known to humanity. The ICC is not a substitute for national courts; the Rome Statute proclaims it is the “duty of every State to exercise its criminal jurisdiction over those responsible for international crimes.”[xxxi] The ICC can only intervene where a State is unable or unwilling to truthfully carry out the investigation and prosecution.[xxxii] Simply put, the ICC will not do a country’s job. Established by Article 1 and 17 of the Rome Statute, this principle of complementarity means the ICC only exercises jurisdiction with the help of national judicial systems.[xxxiii] Complementarity respects the sovereignty of member states and avoids trampling on their judicial systems by recognizing that domestic courts should handle crimes first. Also, a practical necessity as the ICC is resource-limited and could not possibly prosecute every single atrocity worldwide, reflecting the cooperative nature of international law.

The ICC’s jurisdiction can be divided in four sections: territorial, temporal, material, and personal jurisdiction. Territorially, the ICC may exercise jurisdiction only when crimes occur within the territory of a state party (or to a non-party state that has accepted the Court’s authority, such as Ukraine presently).[xxxiv]  Temporally, the Court has jurisdiction only with respect to crimes committed after the entry into force of the Rome Statute.[xxxv] Moreover, crimes within the jurisdiction of the ICC shall not be subject to any statute of limitations.[xxxvi] Materially, the Statute established the ICC’s jurisdiction over the four core international crimes of: (a) the crime of genocide; (b) crimes against humanity; (c) war crimes; (d) the crime of aggression.[xxxvii] Lastly, personally, the ICC has jurisdiction over crimes committed by nationals of state parties to the Rome Statute that are over 18 years old and of a sane mind.[xxxviii] Jurisdiction may also arise in special cases when a situation is referred by the United Nations Security Council.[xxxix]

As of writing, 125 countries are parties to the Rome Statute, meaning many states have still not ratified the Statute, including the United States.[xl] While the establishment of the ICC is a high-standing pinnacle of ICL, its uneven participation demonstrates how it, and international law as a whole, is continually constrained by political realities.

The Enforceability Problem

One of the primary critiques that has shadowed the field of international law since Nuremberg is its perceived lack of enforceability. Many point to the fact that international law, which includes ICL, International Human Rights Law, International Humanitarian Law, and more, has failed to prevent catastrophic human rights abuses such as the persecution of the Rohingya and Armenians, the genocides in Cambodian and Rwandan, the ethnic cleansing in former Yugoslavia, and ongoing alleged violations against Uyghurs and Tibetans in China.[xli] These failures have led to significant doubt about the effectiveness of international law, particularly given many states’ refusal to uphold their international obligations or comply with ICC investigations. While states rely on police forces or government agencies to enforce domestic law, the UN and ICC lack a similar mechanism. While the ICC relies entirely on State Parties to execute arrest warrants, the strongest enforcement system available to the UN is the Security Council  (“UNSC”), which, acting under Chapter VII of the UN Charter, may impose mandatory sanctions to attempt to rectify situations such as acts of aggression or breaches of peace.[xlii] These sanctions may be “economic (such as a trade embargo against a country threatening the peace), diplomatic (such as severance of diplomatic relations) or military (the use of armed force to maintain or restore international peace and security).”[xliii] 

The problem with the UNSC, however, is that its members (United States, People’s Republic of China, Russia, France, and Britain) are often mired in geopolitical disputes and therefore struggle to reach consensus on effectively enforcing international law, especially as they all possess veto power.[xliv] China, for example, has blocked UNSC action on Myanmar and would veto any action regarding its own record in Xinjiang or Tibet; likewise, Russia has blocked resolutions on Ukraine, and the United States would likely oppose scrutiny over its own military conduct in Venezuela or Yemen.[xlv] Additionally, even amid recent movements toward protectionism, states possess vested trade interests in one another and often prioritize economic interests over human rights.[xlvi] This is evident in the fact that, despite widespread allegations of abuse, 37 countries defended China’s “remarkable achievements” before the UN Human Rights Council in 2019.[xlvii] States consistently act in self-interest, disregarding their international obligations and often avoiding consequences for serious human rights violations. Moreover, as the ICC investigates individuals, and not states, its range of enforcement mechanisms is even more limited. Even in a perfect world where the UNSC is united, historically UN sanctions regimes have overwhelmingly targeted states and not individuals (since 1966, the Security Council has established 31 sanctions regimes), thus leaving the ICC, as noted, to the mercy of state parties to arrest individuals.[xlviii] Despite the ICTY and ICTR’s eventual success in securing arrests, the enforceability problem remains in ICL and international law more broadly, tightly bound with geopolitics and self-interest.

Conclusion

A story of both progress and limitation, the birth and evolution of ICL reflects a struggle as old as time. From the bold experiments of Nuremberg and Tokyo, through decades of Cold War paralysis, to the revival of international justice in the tribunals for Yugoslavia and Rwanda, each step built momentum towards a permanent court. The Rome Statute and establishment of the ICC crystalized this momentum and the ICC’s vision: that certain crimes offend not just the victims or their states, but humanity itself. Issues persist, however, as the uneven ratification of the Rome Statute and the ICC’s reliance on state cooperation mean ICL is persistently at the mercy of geopolitics. ICL therefore stands as both a remarkable achievement in the struggle for global justice but also as an ongoing experiment, constantly tested by the shifting balance between law, power, and the pursuit of accountability. As the experiences of the ICTY and ICTR show, the true measure of ICL’s strength lies not in theory but in its response to reality, today embodied in the struggles of Myanmar and Ukraine.

Endnotes

[i] Ilias Bantekas and Susan Nash, International Criminal Law (London: Cavendish Publishing, 2003) at 495 [Bantekas].

[ii] Ibid at 8.

[iii] Ibid.

[iv] Ibid at 497.

[v] Ibid at 498-499.

[vi] Ibid at 498.

[vii] Federico José Quinzena, “International Criminal Law as a Cold War-Inflected Project” in forthcoming Matthew Craven, Sundhya Pahuja & Gerry Simpson, eds, The Cambridge History of International Law, Volume 11: Global International Law during the Cold War (Cambridge University Press), online: <https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4794012> at 8.

[viii] Ibid at 9.

[ix] K.J. Heller, The Nuremberg Military Tribunals and the origins of International Criminal Law (Leiden: Leiden University Press, 2011) at 127 [Heller].

[x] Ibid at 121.

[xi] Charter of the International Military Tribunal for the Far East, 19 January 1946, TIAS No 1589, at s 2.

[xii] Heller, supra note 9 at 104

[xiii] Memorium Nuremberg Trials, “Birth of international criminal law”, online: <https://museums.nuernberg.de/memorium-nuremberg-trials/the-legacy-of-nuremberg/birth-of-international-criminal-law>.

[xiv] International Churchill Society, “The Sinews of Peace (‘Iron Curtain Speech’)”, online: <https://winstonchurchill.org/resources/speeches/1946-1963-elder-statesman/the-sinews-of-peace/>.

[xv] Bantekas, supra note 1 at 513.

[xvi] International Criminal Tribunal for the former Yugoslavia, “ICTY Facts & Figures”, online (pdf): <https://www.icty.org/sites/icty.org/files/images/content/Infographic_facts_figures_en.pdf>.

[xvii] International Criminal Tribunal for the former Yugoslavia, “History”, online: <https://www.icty.org/sid/95>.

[xviii] Ibid.

[xix] Northeastern University School of Law, “International Criminal Tribunal for Rwanda (ICTR)”, online: <https://cglj.org/human-rights-law/international-criminal-law/ictr/> [ICTR].

[xx] Ibid.

[xxi] Bantekas, supra note 1 at 514.

[xxii] Ibid.

[xxiii] United Nations International Residual Mechanism for Criminal Tribunals, “ICTR Milestones”, online: <https://unictr.irmct.org/en/ictr-milestones>.

[xxiv] Ibid.

[xxv] The Prosecutor v Jean-Paul Akayesu (Judgement) [1998] ICTR-96-4-T at para 731.

[xxvi] International Crimes Database, “The Prosecutor v Jean-Paul Akayesu”, online: <https://www.internationalcrimesdatabase.org/Case/50/Akayesu/>.

[xxvii] ICTR, supra note 19.

[xxviii] Ibid.

[xxix] United Nations, “Mechanism Concluding Tasks of Criminal Tribunals for Rwanda, Former Yugoslavia ‘Steadily Advancing on Path of Completion’, President Tells Security Council” (11 June 2024) online: <https://press.un.org/en/2024/sc15724.doc.htm>.

[xxx] Understanding the International Criminal Court (The Hague, Netherlands: International Criminal Court, 2020), online (pdf): <https://www.icc-cpi.int/sites/default/files/Publications/understanding-the-icc.pdf> at 6.

[xxxi] Ibid.

[xxxii] Ibid.

[xxxiii] Rome Statute of the International Criminal Court, 17 July 1998, 2187 UNTS 90 (entered into force 1 July 2002), at s 1 and 17.

[xxxiv] Ibid at s 12.

[xxxv] Ibid at s 11.

[xxxvi] Ibid at s 29.

[xxxvii] Ibid at s 5(a)-(b).

[xxxviii] Ibid at s 25-27.

[xxxix] International Criminal Court, “How the Court works”, online: <https://www.icc-cpi.int/about/how-the-court-works>.  

[xl] International Criminal Court, “The States Parties to the Rome Statute”, online: <https://asp.icc-cpi.int/states-parties>.

[xli] Douglass Cassel, “Does International Human Rights Law Make a Difference” (2001) 2:1 Chicago J Intl L at 122.

[xlii] Frederic L. Kirgis, “Enforcing International Law” (1996) 1:1 American Society of Intl L.

[xliii] Ibid.

[xliv] Oona A. Hathaway and Stewart Patrick, “Can the UN Security Council Still Help Keep the Peace? Reassessing Its Role, Relevance, and Potential for Reform” Carnegie Endowment For International Peace (2 July 2024) online: <https://carnegieendowment.org/posts/2024/07/can-un-security-council-still-help-keep-the-peace?lang=en>.

[xlv] Edith M. Lederer, “Russia and China block UN statement on Myanmar crisis” AP News (28 May 2022) online: < https://apnews.com/article/russia-ukraine-politics-asia-china-032418ad6c63394ce2968dd665f90633>.

[xlvi] Harpreet Kaur, “Aligning trade and human rights” Hinrich Foundation (1 November 2022) online: <https://www.hinrichfoundation.com/research/article/sustainable/aligning-trade-and-human-rights/>.

[xlvii] “37 countries rally around China at top UN human rights body”, AP News (12 July 2019) online: <https://apnews.com/general-news-a2584de07c014e4786a21bcf9f446a40>.

[xlviii] United Nations, “Sanctions”, online: <https://main.un.org/securitycouncil/en/sanctions/information>.