International humanitarian law establishes mechanisms to ensure that its rules are enforced. States are obligated to take steps to prevent violations from happening and to prosecute and punish individuals responsible for the most serious violations. The most serious violations of the Geneva Conventions during an international armed conflict are known as grave breaches, which constitute war crimes. The Geneva Conventions provide a detailed list of grave breaches. They include the willful killing of civilians and captured combatants, torture and other inhuman treatment, and issuing orders that there should be no survivors.
The Geneva Conventions obligate states to punish grave breaches. However, the Conventions do not provide specific penalties or establish a criminal tribunal. States must enact laws to investigate and punish those responsible for war crimes. States must also apprehend individuals alleged to have committed or to have ordered others to commit grave breaches, and either bring them to justice before their own courts or turn them over for trial in another country. Finally states must cooperate with each other in prosecuting offenders during peacetime as well as in war to prevent grave breaches from reoccurring.
The culpability of officers for war crimes that their subordinates commit is known as command responsibility. A military officer or civilian official has direct responsibility for ordering subordinates to commit war crimes, for example ordering that all prisoners be executed. A military authority can also be held responsible if the superior knew or should have known about atrocities committed by a subordinate and failed to take action. An individual found to have command responsibility for the crime committed by a subordinate is deemed equally culpable as the subordinate; that is, if the officer stood by while the subordinate committed murder, the officer is also guilty of murder. Subordinates may still be prosecuted if their commanders are held to be responsible because of command responsibility. Claiming that one was "just following orders" (the doctrine of superior orders) is not a defense to criminal liability, but it may result in the subordinate receiving a lighter sentence.
A nation's criminal law normally only applies to crimes committed within its borders or by its own nationals. War crimes are considered to be crimes of universal jurisdiction. That means that they are so universally recognized as abhorrent that any nation may prosecute the perpetrators, regardless of their nationality, the nationality of the victims or the location of the crime. Currently, few nations have laws that allow them to prosecute persons on the basis of universal jurisdiction.
The international criminal tribunals established for the former Yugoslavia and Rwanda are specifically empowered to prosecute war crimes in the former Yugoslavia and Rwanda, respectively. The proposed International Criminal Court will not have retroactive jurisdiction, meaning it can only prosecute war crimes occurring after its establishment. Even after it is set up, primary responsibility for bringing violators of international humanitarian law to justice will remain with national governments.