War crimes are serious violations of IHL committed during international or non-international armed conflicts. Definitions or lists of war crimes can be found in various legal texts, including the Statute of the International Military Tribunal established after the Second World War in Nuremberg, the Geneva Conventions and their Additional Protocols, the Statutes and case law of the International Criminal Tribunals for the former Yugoslavia and Rwanda, the Rome Statute of the International Criminal Court, and other international and ‘mixed’ tribunals.

Article 8 of the Statute of the International Criminal Court contains a list of war crimes that States drew up in treaty form; it is also a useful guide to the acts that States generally consider to be serious violations of IHL under customary international law. The legislation and case law of various countries also contain definitions of war crimes.

What are war crimes?

The following acts are among those classified as war crimes:
• wilful killing of a protected person (e.g. wounded or sick combatant, prisoner of war, civilian)
• torture or inhuman treatment of a protected person
• wilfully causing great suffering or serious injury to a protected person
• attacking the civilian population
• unlawful deportation or transfer
• using prohibited weapons or methods of warfare
• making improper use of the red cross or red crescent emblem or other protective signs
• perfidiously wounding or killing individuals belonging to a hostile nation or army
• pillage of public or private property.

Although IHL treaties pertaining to non-international armed conflicts do not contain any provisions on the criminalization of serious IHL violations, nowadays it is recognized that the notion of war crimes under customary international law also covers serious violations committed in noninternational armed conflicts. (See Rule 156 of the ICRC’s study on customary IHL and Article 8, paragraph 2 c), d), e) and f) of the Rome Statute.)

What are crimes against humanity and genocide?

International law recognizes other types of crime such as crimes against humanity and genocide. Crimes against humanity are essentially atrocities committed as part of a widespread or systematic attack directed against a civilian population, with knowledge of the attack. Examples of such atrocities include murder, extermination, enslavement, deportation, imprisonment, torture, rape, and persecution on various grounds.

Under the Statute of the International Criminal Court, the crime of genocide covers various “acts committed with intent to destroy, in whole or in part, a national ethnical, racial or religious group, as such.” The acts in question are the following: 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.

States’ obligations: Prosecution or extradition of alleged war criminals

On becoming party to the Geneva Conventions or Additional Protocol I, States undertake to enact legislation necessary to punish persons guilty of what are known as ‘grave breaches’ of the Conventions and the Protocol. States are also bound to prosecute in their own courts any person suspected of having committed a grave breach, or to hand that person over for trial in another State.

A State’s criminal laws generally apply only to crimes committed on its territory or by its own nationals, but States are increasingly passing laws that enable their courts to prosecute crimes committed outside their territory.

Under IHL, States are required to seek out and punish any person who has committed a grave breach of IHL – irrespective of his nationality or the place where the offence was committed. This principle, known as universal jurisdiction, is essential to guarantee that grave breaches are effectively repressed. Universal jurisdiction provides the basis in international law for State laws that enable courts in one State to prosecute persons who have committed international crimes in a different State.

Criminal proceedings for serious violations of IHL, i.e. war crimes including – but not limited to – grave breaches, must in some circumstances be brought by national authorities. The ICRC’s study on customary IHL confirms that States have the obligation to investigate war crimes allegedly committed by their nationals or armed forces, or by others on their territory, as well as other war crimes over which they have jurisdiction. They also have an obligation to prosecute, if appropriate, persons suspected of war crimes.


What is the role of international courts?


The International Criminal Court (ICC), set up by States under the Rome Statute, came into force on 1 July 2002. It represents a milestone in the international community’s fight to end impunity for war crimes, genocide, crimes against humanity and the crime of aggression. Though States have the primary responsibility for prosecuting suspected war criminals, the ICC may act – if the criteria required to establish its jurisdiction are met – when domestic courts are unwilling or unable to do so.


Before the ICC, International Criminal Tribunals for the former Yugoslavia and Rwanda (known as the ICTY and ICTR), were set up by the United Nations Security Council in 1993 and 1994 to try persons accused of committing war crimes during the conflicts in those countries. The Mechanism for International Criminal Tribunals – established by the Security Council on 22 December 2010 – has been tasked with carrying out the essential functions of the ICTY and ICTR after they complete their mandates and with maintaining their legacy.


Penal repression of war crimes is also carried out by a growing number of ‘mixed’ or special courts, established in States such as Cambodia, East Timor, and Sierra Leone. Mixed courts have elements of both domestic and international jurisdiction.


Why are international crimes committed?

This question can be answered in various ways. Some claim that ignorance of the law is largely to blame, that it is a natural consequence of war, or that it is because international law (including IHL) lacks an effective centralized system for imposing sanctions. As a matter of fact, laws are violated and crimes committed during times of war and of peace, and regardless of whether it is national or international jurisdiction that is in force. Even so, simply surrendering to the reality of violations of IHL and halting all action that seeks to gain greater respect for this body of law, and abandoning victims of armed conflicts to their fate is not an option. . That is why violations should be ceaselessly condemned, and steps taken to prevent them and punish those who commit them. The penal repression of war crimes is an important means of implementing IHL, whether at the national or the international level.