International Criminal Law

Author: Annalisa Ciampi

Required knowledge: Subjects and Actors in International Law

Learning objectives: to understand the notion, foundation, purpose and importance of international criminal law

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A. Introduction

International criminal law (ICL) refers to principles and rules of international law for the prevention and repression of international crimes. It is a relatively new branch of international law, which owes its very foundation to the emergence of the principle of individual criminal responsibility in international law.

Under classical international law, with States as the main international actors, individuals could not be held accountable, in the same way as they could not claim international rights. The origin of the principle of individual criminal responsibility lies in the idea that in addition to States, individuals may be held responsible for serious violations of international law. This implies that certain international obligations (the prohibition of war crimes, crimes against humanity, genocide, torture, aggression and others) are not only addressed to States, but also to individuals.

Built heavily on the Law of Armed of Conflict, at its inception, for the identification of the violations which give rise to individual criminal responsibility, ILC continues to draw significantly upon international humanitarian law as well as Human Rights Law – the latter also in relation to the fundamental rights of suspects, accused persons, victims and witnesses and the basic safeguards of a fair trial. International criminal law is thus complementary to these other branches of international law.

ICL emerged rapidly in the aftermath of WWII and underwent tremendous developments during the post-1990 years to become a body of international law which plays an important role in upholding fundamental values shared by the international community.

From a normative point of view, ICL includes both substantive and procedural rules concerning the prosecution of international crimes, which are examined in the subsequent chapters. Substantive rules indicate the prohibited criminal activities, including the subjective elements required for, and the circumstances excluding criminal responsibility (see international crimes). They also either authorise States, or impose upon them the obligation, to prosecute and punish persons accused of such criminal acts (see Domestic Prosecution of International Crimes). Procedural criminal law governs international proceedings before international courts and tribunals, from the investigative and prosecutorial phases to the various stages of international trials (see International Criminal Courts and Tribunals). This is also a field where the distinction between customary international law and treaties matters because the discipline may vary depending on the applicable sources.

B. The Principle of Individual Criminal Responsibility in International Law

The notion of international crimes refers to those criminal activities, harmful to values that transcend the interests of individual state communities, in relation to which a need for repression arises in the international community. Therefore, an international crime can be defined as a criminal activity of an individual in relation to which the international community organises some form of international repression.

The first and most important consequence that international law attaches to the commission of an international crime is the criminal responsibility of the individual who commits it. This is the core of the principle of individual criminal responsibility for international crimes, referred to above. The principle of individual criminal responsibility also operates – where necessary – as an exception to the general rule according to which the activity carried out in the name and on behalf of the State is attributable to the latter and not to the individual concerned (principle of individual criminal responsibility for international crimes committed by State-organs). The rationale for this exception – already affirmed in practice after the First World War with reference to war crimes, then reiterated in numerous subsequent instruments and now certainly part of customary international law – could not be explained more effectively than with the words of the Nuremberg Tribunal:

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.

When an international crime is committed by an individual acting on behalf of the State or the coduct of which is attributable to a State, the principle of individual criminal responsibility constitutes an exception to the general immunities of State organs under international law, including persons in leadership positions (both military and civilian). This applies equally to all persons without any distinction based on official capacity before international criminal courts and tribunals (see e.g. Art. 27 of the Statute of the International Criminal Court). For serving heads of States, however, customary international law keeps open the possibility of impunity in limited circumstances among States. Moreover, in international law, superior orders may not be considered as a defence excluding responsibility for international crimes, but only in mitigation of punishment.

As in national legal systems, also in international law, crimes consist of two elements: a conduct, that is an act or omission contrary to a substantive rule prohibiting or imposing a specific behaviour (actus reus), and a mental element, that is a state of mind directed to or linked to the commission of the criminal act (mens rea). Hence, in international criminal law, the general principle applies that no one may be held accountable for an act he/she has not perpetrated or in the commission of which he/she has not in some way participated. International crimes are often committed by a plurality of persons with the same (co-perpetration) or different modalities of participation (joint criminal enterprise). And, a person may only be held criminally responsible if he/she is somehow culpable for the commission of the crime. It follows that both collective and objective responsibility are ruled out. The principles of legality of crimes and penalties also apply. The principle of legality, in criminal law, means that only the law can define a crime and prescribe a penalty (nullum crimen, nulla poena sine lege).

I. Coexistence of International Criminal Law and State Responsibility

International crimes are crimes committed by individuals, but they may entail, in addition to the individual criminal responsibility of the person(s) concerned, international state responsibility. Individual criminal responsibility arises alongside international State responsibility when the crime is committed by a State-organ and/or is attributable to a State under any of the rules on the attribution to States of internationally wrongful acts.

In this respect, a basic distinction can be drawn between crimes committed by private individuals, crimes generally or necessarily committed by State organs, and crimes that are likely to be committed by individuals either in their private or official capacity. While piracy is a crime typically committed by an individual in his/her private capacity, international terrorism is an example of crime that can be committed by private individuals or groups of individuals and state organs alike. However, most international crimes provided under both international customary and treaty law are generally attributable to States. These are the so-called core crimes – as opposed to so-called treaty-crimes: international crimes such as international drug trafficking and terrorism, the prevention and repression of which is only provided for under conventional rules.

The most ancient category of crimes which are always or generally committed by state organs, are war crimes. Genocide and crimes against humanity also originate, as a rule, from State conduct, either in the sense that their authors are State organs or because they are the result of policies or choices indirectly favoured or supported by a State. The commission of one of these international crimes implies the commission of an internationally wrongful act by the State of which the individual is an organ or to which the conduct in question is attributable, according to the general rules of state responsibility. International criminal responsibility and State responsibility are two forms of responsibility – both internationally relevant – conceptually distinct, with international state responsibility remaining governed by general international rules (or the special regimes that may be applicable in the matter).  

The Draft Articles of International State Responsibility adopted by the ILC in 2001, distinguish between two different categories of international wrongful acts: ordinary wrongful acts and serious breaches of peremptory norms of international law. The latter, which in the previous Draft Articles of 1980 were referred to as “international crimes of states”, include the prohibition of core crimes. They constitute a category of particularly serious wrongful acts to which international law attaches consequences different from and in addition to those arising from ordinary breaches of international law.

Individual and State responsibility may sometimes be difficult to disentangle, as in the case of aggression, where the criminal responsibility of the individual normally depends on the existence of an act of aggression by the State to which the individual belongs. ILC has as its object the individual criminal responsibility and not the international responsibility of the State to whose governmental apparatus the accused belongs. But at the very moment the individual-organ is accused, and eventually found guilty, of a crime of aggression, the State to which the individual belongs is also – implicitly – "accused", and possibly "condemned", as an aggressor State. The need remains, however, to keep the two forms of responsibility distinct. It is desirable that the functions of ILC be limited to individual criminal responsibility – although this may have political implications that are also very significant.

II. Enforcement mechanisms

ICL possesses two main enforcement mechanisms: the so-called direct enforcement system and the indirect enforcement system of ICL. The establishment of an international criminal court or tribunal relates to the direct enforcement system of ICL. The prosecution and punishment of international crimes takes place before international courts or tribunals, directly at the international level. Indirect enforcement mechanisms refer to domestic prosecution and punishment before national courts. In this case, criminal repression is organized by national jurisdictions: States have the power and sometimes the duty to prosecute and, where appropriate, punish perpetrators of international crimes. In relation to core crimes, international law provides for the possibility – if not the obligation – of repression by any State, regardless of the place where the crimes were committed or the nationality of the suspect. This is the principle of universal jurisdiction. Also, international law prevents the application of national statutes of limitations to core crimes. An other system is enforcement by the so-called internationalized or hybrid (mixed) tribunals, which combine features of international and national tribunals. Hybrid (Mixed) Tribunals are dealt with in section B of the Chapter International Criminal Courts and Tribunals.

C. The Historical Evolution of International Criminal Law

I. Before World War II

One of the first and most notable manifestations of the principle of individual criminal responsibility is the Treaty of Versailles, which set the terms ending WWI. The victorious Allies – Britain, France, and Italy and the United States – ultimately agreed to investigate and prosecute the defeated German Emperor Kaiser Wilhelm II. Article 227 of the Treaty of Versailles stated that Kaiser Wilhelm would be tried by an international court for the “supreme crime against international morality and the sanctity of treaties.”

The provision was unprecedented in at least three important respects. First, the very notion of holding a leader responsible for crimes committed in conflict was unprecedented. It was also the first time in history that States imagined the possibility of an international tribunal for the prosecution of an individual, and former Head of State, for international crimes. Kaiser Wilhelm II. was never brought to trial, for the Netherlands refused to hand him over. Thereby, Article 227 of The Treaty of Versailles laid the foundation for the future of international criminal justice, although the trial of Kaiser Wilhelm II. never happened

II. From Nuremberg to The Hague

The international prosecution of crimes against peace began with the Nuremberg and Tokyo trials of the major war criminals following WWII.

1. The Nuremberg Trials

The Nuremberg trials were a series of 13 trials carried out in Nuremberg, Germany, between 1945 and 1949 by a tribunal established under the London Charter of the International Military Tribunal (IMT) by the Allies France, Great Britain, the former Soviet Union and the United States. The Tribunal was endowed with the power to try and punish persons who, acting in the interest of the European Axis countries, whether as individuals or as members of organizations, committed any act falling in the three categories of crimes defined in the London Charter: crimes against peace (including planning, preparing, starting or waging wars of aggression or wars in violation of international agreements), war crimes (including violations of customs or laws of war, including improper treatment of civilians and prisoners of war) and crimes against humanity (including murder, enslavement or deportation of civilians or persecution on political, religious or racial grounds) (Article 6). Among other things, it was determined that: “Leaders, organizers, instigators and accomplices participating in the formulation or execution of a common plan or conspiracy to commit any of the foregoing crimes are responsible for all acts performed by any persons in execution of such plan. civilian officials as well as military officers could be accused of war crimes” (Article 6); “The official position of defendants, whether as Heads of State or responsible officials in Government Departments, shall not be considered as freeing them from responsibility or mitigating punishment” (Article 7); and “The fact that the Defendant acted pursuant to order of his Government or of a superior shall not free him from responsibility, but may be considered in mitigation of punishment if the Tribunal determines that justice so requires.” (Article 8).

The best-known of the Nuremberg trials was the Trial of Major War Criminals, held from November 20, 1945, to October 1, 1946. While Nazi leader Adolf Hitler (1889-1945) committed suicide and was never brought to trial, twenty-four individuals, including Nazi Party officials and high-ranking military officers, were indicted along with six Nazi organizations determined to be criminal (such as the “Gestapo”). The IMT found all but three of the defendants guilty. Twelve were sentenced to death, one in absentia, and the rest were given prison sentences ranging from 10 years to life imprisonment.

The Nuremberg trials were controversial even among those who wanted punishment for the Nazis' main criminals. The main criticism, and the most common defense strategy, was that the crimes defined in the London Charter were examples of ex post facto law; that is, Article 6 criminalized actions committed before the relevant provisions were drafted. Another criticism, and defense, was that the trial was a form of victor’s justice – the Allies were applying a harsh standard to crimes committed by Germans and leniency to crimes committed by their own soldiers. On the other hand, the Nurember Tribunal itself responded that the defendants knew that what that they were doing was wrong and therefore the principle of legality, as a principle of justice, was respected.

2. Tokyo Trials

Nonetheless, the IMT’s trials and findings set a step forward for the development of international criminal law. They were paralleled by the trials of the leaders of the Empire of Japan in Tokyo by the International Military Tribunal for the Far East (IMTFE). The Charter of the IMTFE was issued as an order together with a Special Proclamation by General Douglas MacArthur on 19 January 1946, on behalf of the Allied powers. In addition, the IMT supplied a useful precedent for future prosecution of international crimes by national courts, most notably the 1961 trial of Nazi leader Adolf Eichmann by the Supreme Court of Israel.

3. Developments after Nuremberg and Tokyo

The experience of the IMT and the IMTFE inspired the Convention on the Prevention and Punishment of the Crime of Genocide and the Universal Declaration of Human Rights, adopted by the United Nations General Assembly on 8 and 10 December 1948 respectively, as well as the four Geneva Conventions on the Laws and Customs of War adopted on 12 August 1949 by the Diplomatic Conference for the Establishment of International Conventions for the Protection of Victims of War. The International Law Commission (ILC) codified the Principles of international law recognized in the Charter of the Nürnberg Tribunal and in the Judgment of the Tribunal, in 1950. The General Assembly of the United Nations entrusted the ILC also with the task of drafting a Statute for the establishment of an international criminal tribunal, together with a code of crimes, the so-called Code of Crimes Against Peace and Security of Mankind. The two projects were interrelated, and the failure of the latter brought about a stalemate also in the works for draft statute. The Cold War prevented any progress.

4. International Criminal Courts and Tribunals

It was only in 1989 that the General Assembly asked the ILC once again to draft a statute for the institution of an international criminal court. The end of the Cold War also made it possible to establish two ad hoc international criminal tribunals as subsidiary organs of the UN Security Council: the International Criminal Tribunal for the former Yugoslavia (ICTY) and the International Criminal Tribunal for Rwanda (ICTR). During its mandate, which lasted from 1993 to 2017, the ICTY prosecuted those responsible for serious violations of international humanitarian law committed in the territory of the former Yugoslavia since 1991, in accordance with United Nations Security Council resolution 827 (1993) and the Statute annexed thereto. The ICTR, established by Security Council resolution 955 (1994), prosecuted those considered most responsible for genocide and other serious violations of international humanitarian law committed in the territory of Rwanda and neighbouring States in 1994.  

The ILC eventually approved a draft statute in 1994, which provided the basis for the further works which were entrusted to the Preparatory Committee (Prep Com), an ad hoc group of people established by the General Assembly for working on the statute for an international criminal court, taking as the basis of their work the draft statute of the ILC. The Prep Com produced in turn another draft. This text was the basis of the further negotiations, which took place in Rome in 1998 and finally resulted in the adoption by 120 States of the Statute of the International Criminal Court (ICC), on 17 July 1998. The Rome Statute entered into force on 1 July 2002 among the first 60 States that ratified it, making operational the first permanent international criminal court, with its seat at The Hague.

The ICTY and the ICTR terminated their mandate on 31 December 2017 and 2015, respectively, following the establishment by the Security Council of the International Residual Mechanism for Criminal Tribunals to ensure that the closure of the two pioneering ad hoc tribunals does not open the way for impunity.

The ICC (on which see International Criminal Courts and Tribunals, section B) is a functioning institution.

Further Readings

• A. Cassese, P. Gaeta, Cassese's International Criminal Law, 3rd ed. (Oxford University Press 2013)
• R. Cryer, D. Robinson, S. Vasiliev, An Introduction to International Criminal Law and Procedure, 4th ed. (Cambridge University Press 2019)

Further Resources

• Judgment at Nuremberg, film directed by S. Kramer (1961)
• Nuremberg, film directed by Y. Simoneau (2000)

Conclusion

Albeit a relatively new branch of international law, international criminal law has become of prominent importance with the establishment of the International Criminal Court in 1998 and in subsequent years. It is complementary to other branches of international law, such as human rights and international humanitarian law.