A law can only be applied to an act that occurs after the law was adopted. This is a well-established legal principle, derived from the adage that ignorance of the law is no excuse.
In domestic criminal law, the principle of non-retroactivity is applicable to the definition or determination of both felonies and misdemeanors and to the scale of penalties and sentences incurred.
In times of conflict, due to occupation of territory or capture, individuals may find themselves faced with the question of the applicability of laws that are unknown to them. The legal principle that is respected in this case derives from the general principle of non-retroactivity: the new law (in this case, the foreign law) may not impose higher penalties or establish offenses that were not foreseen in the domestic law of these persons.
In all situations, it is important to remember that a law that has not been officially enacted and published is not valid. The date before which non-retroactivity is applicable is the date at which the law was officially enacted—in other words, the date at which it was promulgated and published.
This principle (also known as freedom from ex post facto laws, or nullum crimen sine lege ) thus establishes that a law may not be applied to criminal acts that were committed before the law was enacted. It follows that a heavier penalty may not be imposed than the one that was applicable at the time the act was committed. However, if a new law was adopted after the act was committed that provides for the imposition of a lighter penalty, the offender must benefit from it.
International law also recognizes the non-retroactivity of criminal laws and punishment for criminal acts as a fundamental judicial guarantee (Art. 15 of the International Covenant on Civil and Political Rights). This principle is also integrated into the Geneva Conventions: a person may not be prosecuted for an act or omission that did not constitute a criminal offense under the national or international law to which he or she was subject at the time the act was committed (GCIII Art. 99; GCIV Arts. 65, 67; API Art. 75; APII Art. 6). ▸ Judicial guarantees
This principle is reflected in the Statute of the International Criminal Court (ICC). The Court has jurisdiction only over crimes committed after its Statute enters into force for the State concerned, that is, on 1 July 2002 (Art. 11 of ICC Statute).
Until now, the only case in which an international tribunal could judge crimes committed before the tribunal was created is in the case of war tribunals, such as those set up in Nuremberg and Tokyo after World War II and the ad hoc International Criminal Tribunals set up by the Security Council in 1993 and 1994 for the former Yugoslavia and Rwanda. Even in such situations, the tribunals can only judge acts that were already considered crimes when they were committed. At the time of the creation of the International Criminal Tribunal for the Former Yugoslavia, the Secretary-General of the UN reaffirmed that the ICTY would “apply rules of international humanitarian law which are beyond any doubt part of customary law” (Report of the Secretary-General under Security Council Resolution 808, Doc. S/2504, 3 May 1993). ▸ International Criminal Tribunals
For Additional Information: Bassiouni, Cherif. Introduction to International Criminal Law . Ardsley, NY: Transnational, 2003, 800p.