The “Core” International Crimes

By Marco Sutto

From "The CoESPU MAGAZINE" no. 3 - 2020

Section: "Constraints and Restraints as Limitation of Freedom of Action in Performing a Mission, page 64

DOI Code: 10.32048/Coespumagazine3.20.6

International criminal law (ICL) is a quite new and constantly developing branch of public international law, which deals with the criminal responsibility of individuals for the most serious violations of international human rights and humanitarian laws. ICL, identifying a certain number of “international crimes”, wants to expose perpetrators of such serious violations to personal criminal liability and provides for criminal sanctions that apply to all offenders.

The concept of “international crimes ” is not defined by a universally accepted formulation,   however they are usually referred to as “breaches of international rules entailing the personal criminal liability of the individuals concerned (as opposed to the responsibility of the State of which the individuals may act as organs)”[1], “crimes that involve direct individual criminal responsibility under international law”[2] or even “punishable acts or conduct proscribed by international law”[3].

ICL outlines four main categories of international crimes: genocide, crimes against humanity, war crimes and the crime of aggression. The latter are defined as ‘core’ international crimes to distinguish them from other categories crimes such as terrorism and piracy (to just name a few) which are still object of controversy among the members of the international community.

Criminal accountability for those “core crimes” is considered by the international community of fundamental importance with regard to respect for the rule of law, deterrence of future violations, and the provision of redress and justice for victims.

These criminal conducts are considered to affect the international community as a whole and, consequently, all states have an interest to prevent the occurrence of these particularly heinous crimes and in holding the perpetrators accountable. Indeed, perpetrators of international crimes may be convicted on the basis of their own direct acts or omissions, or when ordering and facilitating a crime.  This includes those who directly commit the crimes as well as those who, at the highest political and military levels, are involved in the planning and authorization of such acts. Thus, the individual criminal responsibility for international crimes can be held in parallel with the responsibility of the state.

The international crimes have been defined over time in a range of international conventions and agreements, beginning with the first Hague Conventions, at the end of the 19th century, which established rules for military conduct during wartime, up to the Rome Statute[4] that, in 1998, established the International Criminal Court (ICC) with jurisdiction over the four “core crimes” (genocide, crimes against humanity, war crimes and the crime of aggression.)

It is on the base of the Rome Statute provisions, which represent the most comprehensive modern codification of international crimes, that the following paragraphs will synthetically explore the features the four “core crimes”.


Genocide is defined by the Rome Statute as one of the following acts : (a) Killing members of the group; (b) Causing serious bodily or mental harm to members of the group; (c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; (d) Imposing measures intended to prevent births within the group; (e) Forcibly transferring children of the group to another group, committed with “the intention to destroy, in whole or in part, a national, ethnical, racial or religious group”[5].

Genocide is essentially considered an attack upon human diversity[6]. The term was crafted with the Holocaust in mind, it is composed of the Greek word ‘geno’ (tribe or race) and the Latin verb ‘caedere’ (to kill)[7]. The essence of genocide is the destruction of the cohesion and moral dignity of a group as collective entity, as an element of international society.[8]

In the Nuremberg judgment the Holocaust was punished under the notion of ‘crimes against humanity’, which includes persecution and extermination. Only one year after the Nuremberg judgment, in 1946, the UN General Assembly adopted a resolution in which it ‘affirmed’ that genocide is a crime under international law[9]. The UN Convention on the Prevention and Punishment of the Crime of Genocide eventually defined the crime as an independent conduct in 1948[10]. The definition of the Convention was then reproduced in the Statutes of international criminal courts and tribunals, such as the ad hoc tribunals for the former Yugoslavia[11] , Rwanda[12] and, lastly, the ICC.

The spirit of the crime of genocide lies in the attack on specific protected groups of victims. It can only be committed against national, ethnic, racial or religious groups[13]. Other groups, such as political or cultural groups, are not recognized as protected groups per se[14]. Genocide does not require the actual destruction of a protected group. However, according to the Convention, the enumerated acts must be committed with the ‘intent’ of the perpetrator to destroy the group in whole or in part’ (‘specific intent’). Moreover, Genocide is the only crime in which incitement is expressly prohibited[15]. The prohibition takes into account that genocide is often spread through mass mobilization. While drafting the Genocide Convention the delegates of the State parties decided to criminalize public and direct incitement to genocide in order to counter emerging patterns of genocide and take into account the specific risks of incitement of an indeterminate group of persons (e.g. through speeches, radio, press or other media)[16].

As cultural factors, such as social, historical and linguistic features, are often necessary to explain whether a group qualifies as a racial, ethnic, religious or national group, the definition of the extent to which cultural destruction may amount to genocide has generated a long debate[17]. As a matter of facts, the cultural dimension play an important role in the determination of genocide and, technically, the actus reus of genocide is not confined to killing. Physical and biological destruction are then often complemented by the elimination of cultural features, property or symbols.

Crimes against humanity

Crimes against humanity are identified by the art.7 of the Rome Statute, which contains their most comprehensive modern treaty codification[18], as the following acts: (a) Murder; (b) Extermination; (c) Enslavement; (d) Deportation or forcible transfer of population; (e) Imprisonment or other severe deprivation of physical liberty in violation of fundamental rules of international law; (f) Torture; (g) Rape, sexual slavery, enforced prostitution, forced pregnancy, enforced sterilization, or any other form of sexual violence of comparable gravity; (h) Persecution against any identifiable group or collectivity on political, racial, national, ethnic, cultural, religious, gender as defined in paragraph 3, or other grounds that are universally recognized as impermissible under international law, in connection with any act referred to in this paragraph or any crime within the jurisdiction of the Court; (i) Enforced disappearance of persons; (j) The crime of apartheid; (k) Other inhumane acts of a similar character intentionally causing great suffering, or serious injury to body or to mental or physical health. Paragraph 1 of art.7 requires the mentioned acts, part of which are also recognized as common crimes by many national legal frameworks, must be committed as part of a widespread or systematic attack directed against any civilian population.

It appears clear that the concept of crimes against humanity retains some features of genocide, such as the idea of extermination. However, crimes against humanity differ from genocide, as while the latter focuses on the collective nature of the victims as a group, identified by nationality, ethnicity, race or religion, they are inclined to penalize the collective nature of the perpetration of crimes[19]. Crimes against humanity are attacks on civilian populations that are at risk because of their presence in the targeted population.

The basic idea is that, where exists a collective action of an organization that causes harm to the civilian population throughout a widespread or systematic violence, a crime is no longer simply an ordinary crime under domestic law but an international crime.  Therefore, the peculiar element that distinguishes crimes against humanity from domestic crimes is the context in which they are committed, as part of a widespread or systematic attack against the civilian population.

Marking a significant development in international law, crimes against humanity were codified, for the first time, in the Charter of the Nuremberg Tribunal. Indeed, until then, the conduct of a state towards its own citizens was strictly considered a matter of internal affairs. Nevertheless, in the first codification, the crimes against humanity could not be charged independently of a nexus to other crimes, they had to be linked to war crimes or crimes against peace (aggression). As seen in Statutes of major international criminal courts and, lastly, in the Rome Statute,  the concept of crimes against humanity was then unbound from its war-related nexus and was developed more in line with the human rights tradition. Indeed, Crimes against humanity can now be committed in both the context of armed conflict and in peacetime. The reference to the concept of ‘civilians’ in the definition of the crime is the only reminiscence of the historical linkage to war crimes.

Crimes against humanity could be differentiated in two categories of offences. The first one encompasses the so-called murder-type offences. They include murder, extermination, enslavement, deportation or forcible transfer of population, torture, acts of sexual violence or enforced disappearance of persons. Some but not all of them are criminal offences in national legal systems.  They were banned internationally because of their cruelty and barbarity. The second type of offences is ‘persecution’-related. They are typically  geared at persecution of a specific group of people on racial, religious or political grounds[20]   and often may not be considered criminal or even prohibited in national legal systems.

The notion of attack against civilian population of the crimes against humanity is understood in an extensive way, including the use of armed force and any form of mistreatment or discriminatory practices. An attack is considered ‘widespread’ if it is conducted on a large scale and, even if there is no specific numerical threshold, it results in a large number of victims[21] .  The term ‘systematic’ used to define the attacks refers to their organized nature, such as the repetition of similar criminal conduct on a regular basis.[22] In absence of the repetitive element, the systematic nature of the attacks could be also substantiated by the existence of a plan concerning attacks or other factors such as, for instance, the existence of a particular policy or ideology to destroy or weaken a community, discriminatory measures, measures changing the demography of the population, or the involvement of high-level political and/or military leaders in the establishment of the plan[23].

War crimes

War crimes are the oldest category of international crimes. They are grounded in international humanitarian law (IHL), traditionally known as jus in bello (the law of war), an independent branch of public international law. IHL regulates the conduct of parties engaged in an armed conflict and seeks to minimize suffering and harm. It is based on a balance between military necessities and humanitarian considerations. Indeed, in armed conflict, certain acts of violence, such as attacking enemy’s military objectives, are allowed (lawful) and others prohibited (unlawful).   International humanitarian law regulates both lawful and unlawful acts of violence reconciling the two different perspectives, on one side, the humanitarian commitment ‘to prevent or mitigate suffering’, on the other, the pragmatic warfare necessity of overcoming the enemy.

Historically, a turning point in the codification of international humanitarian law has been identified in the battle of Solferino[24]  and the subsequent issue of the first Geneva Convention[25] for the amelioration of the condition of wounded combatants. The body of IHL rules was then complemented by the ‘Hague law’[26], on the rights and obligations of belligerents in the conduct of military, and the ‘Geneva law’[27] designed to protect victims of armed conflict and specific categories of persons, such as prisoners of war, detainees, civilians and humanitarian aid workers. Nowadays, nearly every state in the world has agreed to be bound by IHL provisions and the core of them is considered as customary international law.

However, only specific and serious violations of international humanitarian law are criminalized as “war crimes”. The initial IHL provisions failed to specify whether a violation entailed criminal responsibility and the “War crimes law” was developed incrementally and through practice in the twentieth century.  Even the Geneva Conventions and its Protocols, by qualifying the so-called grave breaches as ‘war crimes’ , created a certain initial confusion from a conceptual point of view, since the idea of “grave breaches” implies a hierarchy, whereby certain violations are considered grave enough to qualify as crimes, whilst others do not. One of the key prerequisites of a war crime is that the crime is connected to the armed conflict. This is a necessary requirement to distinguish war crimes from ordinary offences[28].

Upon war crimes is established a universal jurisdiction[29], which entitles a State to prosecute offenders even in the absence of any link between the crime committed and the prosecuting state. In order to make this principle effective, States are required to establish universal jurisdiction for war crimes in their national legislation. The basis for the assertion of universal jurisdiction over war crimes is found in both treaty law and in customary international law.[30] The ICC Statute consider the war crimes in art. 8 providing a comprehensive list of them and containing an additional element that specifies the ICC has jurisdiction ‘in particular’ when war crimes are ‘committed as part of a plan or policy or as part of a large-scale commission of crimes’.

The large majority of war crimes can be traced back to the violation of certain fundamental principles of international humanitarian law grounded in the protection of persons and property[31]. A first fundamental principle is the principle of protection of non-combatants that requires parties to an armed conflict to treat civilians, prisoners of war and wounded or sick former combatants humanely. A second key principle is the principle of distinction. It requires parties to a conflict at all times to distinguish between civilians and combatants and direct the attacks only against combatants and military objects. They must not be directed against civilians or civilian objects, such as churches, hospitals or private residences that are not used for military purposes. The ICC Statute also expressly prohibits attacks on humanitarian assistance and peacekeeping missions, as long as they are entitled to civilian protection[32]. A third fundamental principle under international humanitarian law is the principle of proportionality. It prohibits an attack on a military objective if such an attack may be expected to cause excessive collateral damage (such as loss of civilian life, injury to civilians and damage to civilian objects) in relation to the concrete and direct military advantage anticipated. Lastly, the fourth fundamental principle is the prohibition on employing weapons, ammunition, materials and methods of warfare of a nature to cause superfluous injury and unnecessary suffering to members of the armed forces and civilians who directly participate in hostilities.

To be held accountable of war crimes the required mental elements may differ in terms of their thresholds. On this matter, the ICC sets a relatively high mens rea standard stating that, unless otherwise provided, intent in relation to consequence exists only if the person ‘means to cause that consequence or is aware that it will occur in the ordinary course of events’ [33].

Crime of aggression.

Aggression is one of the most controversial crimes in international criminal law[34]. Likewise war crimes, it is essentially connected to armed violence. Still, aggression does not involves a breach of the jus in bello, but a criminalization of certain forms of recourse to force (jus ad bellum). Aggression is usually defined as the most serious and dangerous form of illegal use of force by a state against the sovereignty, territorial integrity or political independence of another state[35].

The crime of aggression highlights the trend towards a jus contra bellum in the international legal order, characterized by the restriction of the use of armed force in international relations. Despite that, the crime has a troubled past and in most historical cases, it has been prosecuted after the fact.

In the first version of ICC Statute the crime of aggression was just symbolically included in Article 5 but its exercise of jurisdiction remained pending on the formulation of a proper definition. Only after years of debates and negotiations, at the Kampala Review Conference (2010), states reached agreement on a definition of the crime and the conditions under which the Court can exercise jurisdiction. The new definition identifies as  “crime of aggression” the planning, preparation, initiation or execution, by a person in a position effectively to exercise control over or to direct the political or military action of a State, of an act of aggression which, by its character, gravity and scale, constitutes a manifest violation of the Charter of the United Nations[36]. The Kampala definition describes aggression as a leadership crime and extends individual criminal responsibility from the traditional concept of ‘war of aggression’ to ‘acts of aggression’ according with General Assembly Resolution 3314 definitions[37]. The idea of individual criminal responsibility is closely linked to unlawful state action in international relations. Therefore, an individual cannot incur responsibility in the absence of an act of aggression under international law.[38]

In practice, types of aggression may vary from mere violations of sovereignty (e.g. targeted air strikes) to interventions with on-site presence or other unlawful uses of force. These acts may involve high civilian casualties or loss of life and disturb peace and security. In other cases, they may cause limited human damage, or even be exercised with the intent to protect peace and security or human rights.[39]

However, several are the factors that limit the definition of a conduct as “act of aggression”. As stated in art.8 bis of the ICC Statute, the crime of aggression requires an act which ‘by its character, gravity and scale’ constitutes ‘a manifest violation of the Charter’. These factors distinguish the crime of aggression from general violations of the prohibition of the use of force, resulting in the fact that not every illegal use of force entails individual criminal responsibility for aggression.

For the crime of aggression, compared to the other crimes, the ICC has limited jurisdiction in  state referral or proprio motu proceedings[40]. Indeed, the Court cannot exercise jurisdiction over persons of states which are not party to the Rome Statute or have not accepted the aggression amendment[41]. In these circumstances, exercise of jurisdiction over aggression is tied to the prospect of a Security Council referral[42]. Moreover, another peculiar feature of the this crime under the Rome Statute entails that States parties do not enjoy protection by the ICC against crimes of aggression committed by non-state parties against them (i.e. on their territory), although they enjoy such protection for other categories of crimes[43].

In conclusion, as highlighted with this brief analysis of the “core crimes”, it appears clear that the approaches towards international crimes are quite new and still in progress. International criminal law has evolved significantly since its first steps in the late eighteenth and early nineteenth centuries and the creation of a permanent Court, the ICC, able to exercise an international jurisdiction over the four “core crimes” represents, despite its legal and practical limitations, an achievement of paramount importance in the advancement of human rights protection.  The modern interpretation of international criminal law has proved able to develop in a dynamic way covering both the ‘public’ and ‘private’ sides of violence thus protecting different interests: state interests, the autonomy and dignity of individuals and group rights.


[1] A. Cassese, International Criminal Law, Oxford University Press: Oxford 2003.

[2] G. Werle, Principles of International Criminal Law, T.M.C. Asser Press: The Hague 2005.

[3] Terje Einarsen , The Concept of Universal Crimes in International Law: Torkel Opsahl Academic EPublisher Oslo2012

[4] Even ICC-International Criminal Court Statute.

[5] Rome Statute, Article 6

[6] Stahn, C. (2018). A Critical Introduction to International Criminal Law. Cambridge: Cambridge University 2018

[7] first officially used in 1944 by Polish-Jewish lawyer R. Lemkin in his “Axis Rule in Occupied Europe” (Washington, DC: Carnegie Endowment for International Peace, 1944).

[8] Ibid,  Origin of genocide

[9] See GA Res. 96 (I), UN Doc. GA/Res/96(I), 11 December 1946.

[10] Art. 2 Convention on the Prevention and Punishment of the Crime of Genocide, 9 December 1948, 78 UNTS 1021

“In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:

(a) Killing members of the group;

(b) Causing serious bodily or mental harm to members of the group;

(c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;

(d) Imposing measures intended to prevent births within the group;

(e) Forcibly transferring children of the group to another group.”

[11] Art. 4, Updated Statute of the International Criminal Tribunal for the Former Yugoslavia, S/Res/827 (1993) of 25 May 1993.

[12] Art. 2, Statute of the International Tribunal for Rwanda, S/Res/955 (1994) of 8 November 1994.

[13] On difficulties of the concept of race, see C. Lingaas, ‘Elephant in the Room: The Uneasy Task of Defining “Racial” in International Criminal Law’ (2015) 15 International Criminal Law Review 485.

[14] Stahn, C. (2018). A Critical Introduction to International Criminal Law- Nature of the crime of genocide. Cambridge: Cambridge University

[15] Art.3 Convention on the Prevention and Punishment of the Crime of Genocide, 9 December 1948 : The following acts shall be punishable:

(a) Genocide; (b) Conspiracy to commit genocide; (c) Direct and public incitement to commit genocide; (d) Attempt to commit genocide; (e) Complicity in genocide.

[16] The Russian Delegate stated: ‘It was impossible that hundreds of thousands of people should commit so many crimes unless they had been incited to do so … The peoples of the world would indeed be puzzled if … those who incited others to commit the concrete acts of genocide, were to remain unpunished.’ Summary Records of the meetings of the Sixth Committee of the General Assembly, 21 September‒10 December 1948, Official Records of the General Assembly, statements by Mr Morozov, 241.

[17] See generally, E. Novic, The Concept of Cultural Genocide (Oxford: Oxford University Press, 2016); L. Bilsky and R. Klagsbrun, ‘The Return of Cultural Genocide?’(2018) 29 EJIL 373–396. Russia made a proposal to cover it in the Genocide Convention as follows: ‘In this Convention genocide also means any deliberate act committed with the intent to destroy the language, religion or culture of a national, racial or religious group on grounds of national or religious origin, or religious beliefs such as: (a) Prohibiting the use of the language of the group in daily intercourse or in schools or the printing and circulation of publications in the language of the group; (b) destroying or preventing the use of libraries, museums, schools, historical monuments, places of worship or other cultural institutions and objects of the group.’ See General Assembly, Agenda Item 32, UN Doc A/766, 5 December 1948, in H. Abtahi and P. Webb, The Genocide Convention: The Travaux Préparatoires (Leiden: Brill Nijhoff 2008), 2039.

[18] Stahn, C. (2018). Origin- Crimes against Humanity.

[19]Stahn, C. (2018). Citing  J. D. Ohlin, ‘Organizational Criminality’, in E. van Sliedregt and S. Vasiliev, Pluralism in International Criminal Law (Oxford: Oxford University Press, 2014), 118.

[20] See generally F. Pocar, ‘Persecution as a Crime under International Criminal Law’ (2008) 2 Journal of National Security Law & Policy 355.

[21]  Idib. Citing  ITY-Prosecutor v. Blaškić, IT-95–14, Judgment, 3 March 2000, para. 206 (Blaškić Trial Judgment).

[22] Idib. Citing  ITY Kunarac Appeal Judgment, para. 94-95.

[23] Idib. Citing Blaškić Trial Judgment, para. 203.

[24] The Battle of Solferino (referred to in Italy as the Battle of Solferino and San Martino) on 24 June 1859 resulted in the victory of the allied French Army under Napoleon III and Sardinian Army under Victor Emmanuel II (together known as the Franco-Sardinian Alliance) against the Austrian Army under Emperor Franz Joseph I.

[25] The First Geneva Convention for the Amelioration of the Condition of the Wounded in Armies in the Field, 22 August 1864.

[26] 1899 and 1907 Hague Conventions on means and methods of combat.

[27] The four Geneva Conventions of 1949.

[28] For instance, there is no reason why crimes committed by certain civilians not taking part in hostilities against other civilians should automatically qualify as war crimes.

[29] Universal jurisdiction refers to the assertion of jurisdiction over offences regardless of the place where they were committed and the nationality of the perpetrator or the victim.

[30] ICRC-ADVISORY SERVICE ON INTERNATIONAL HUMANITARIAN LAW-Universal jurisdiction over war crimes –(03/2014): “The treaty basis for the assertion of universal jurisdiction was first introduced by the four Geneva Conventions of 1949 for the protection of war victims in relation to those violations of the Conventions defined as grave breaches. Under the relevant article of each Convention (Arts 49, 50, 129 and 146, respectively), States are required to search for alleged offenders “regardless of their nationality,” and either bring them before their own courts or hand them over for trial by another State Party which has made out a prima facie case. …..While the relevant treaty law provisions are restricted to grave breaches, universal jurisdiction in customary international law may be regarded as extending to all violations of the laws and customs of war which constitute war crimes.”

[31] Stahn, C. - Types of War Crimes - A Critical Introduction to International Criminal Law. Cambridge: Cambridge University 2018.

[32] Arts. 8 (2) (b) (iii) and 8 (2) (e) (iii), ICC Statute.

[33] See Art. 30. ICC Statute.

[34] Stahn, C. -1.3.4 The Crime of Aggression.

[35] See GA Resolution 3314 of 14 December 1974.

[36] Article 8 bis3. 

[37] The UN General Assembly adopted Resolution 3314 in 1974, in order to guide the practice of the Security Council in relation to findings on aggression. The Resolution remained minimal in relation to individual criminal responsibility, however. It simply reconfirms the Nuremberg holding that a ‘war of aggression’ constitutes a crime of aggression (Art. 6 of GA Res. 3314 ).

[38] Stahn, C. citing Jens David Ohlin ‘Organizational Criminality’, 107, 118.

[39] Stahn, C. State Act of Aggression.

[40] See artt. 13 and 15bis ICC Statute.

[41] Which still represent the majority of the International community. Currently only 39 state parties ratified the amendment (

[42] See art. 15 ter ICC Statute.

[43] Art. 8 bis and 12 ICC Statute.