International criminal law has seen an enormous growth in the past two decades with the creation of international criminal tribunals and the permanent International Criminal Court.  These judicial bodies have all contributed to the definition and expansion of international criminal law principles.

One such area of law which has developed during this time is the principle of nullum crimen sine lege or nullum poena sine lege (NCSL).  Translated, this means “no crime without law” or “no punishment without law.” This principle is meant to prevent the prosecution and punishment of a person for an act which at the time of its occurrence was not a law and the accused had no reasonable belief that his or her act was criminal. 

NCSL is an extremely important principle in international criminal law because acts punished by international criminal tribunals are often of ambiguous legality in the conflict situations in which they were committed.  At the outset of proceedings, tribunals define the scope of the alleged acts and the context in which they were committed.  NCSL often is used as a first-line defense in international criminal proceedings and is typically asserted and litigated by defense teams.

This principal is codified in international treaties. The Universal Declaration of Human Rights sets forth in Article 11 that “No one shall be held guilty of any penal offence on account of any act or omission which did not constitute a penal offence, under national or international law, at the time when it was committed. Nor shall a heavier penalty be imposed than the one that was applicable at the time the penal offence was committed.”  This definition is similarly seen in the International Covenant on Civil and Political Rights, the European Convention for the Protection of Human Rights and Fundamental Freedoms, and the American Convention on Human Rights.  It is also defined in the Rome Statue of the International Criminal Court in Article 22: “A person shall not be criminally responsible under this Statue unless the conduct in question constitutes, at the time it takes place, a crime within the jurisdiction of the Court."   

While treaties lay out the principle of NCSL, cases brought before war crimes tribunals have shaped and defined the application of NSCL in international criminal law. The International Criminal Tribunal for the Former Yugoslavia (ICTY) dealt with this issue during its very first trial.  In  Prosecutor v. Tadić,  Case No. IT-94-1-T, Defense Motion for Interlocutory Appeal on Jurisdiction, Oct. 2, 1995, the defense argued that the accused could not be tried for violations of crimes against humanity because the definition of this crime applied to international armed conflict. Applying this definition to internal armed conflict would violate the NCSL principle.

The Appeals Chamber stated that this nexus requirement was eliminated from the Nuremberg Charter's definition of crimes against humanity and additionally that "the obsolescence of the nexus requirement is evidenced by international conventions regarding genocide and apartheid, both of which prohibit particular types of crimes against humanity regardless of any connection to armed conflict.”

The Appeals Chamber also emphasized the importance of the principle of NCSL by remarking that: "the only reason behind the stated purpose of the drafters that the International Tribunal should apply customary international law was to avoid violating the principle of nullum crimen sine lege in the event that a party to the conflict did not adhere to a specific treaty."  This set forth that the ICTY was upholding NCSL as customary law and treaties are to be applied to determine if the principle of NCSL has been met.

The Special Court for Sierra Leone examined this issue of reviewing customary law for purposes of NCSL in Prosecutor v. Norman, Case No. SCSL-2004-14-AR72(E), Decision on Preliminary Motion Based on Lack of Jurisdiction (Child Recruitment, May 31, 2004).  The tribunal examined whether child soldier recruitment constituted criminal conduct and punishable under international and national law to an extent that would show customary practice meeting NCSL standards.  Examining the law in Sierra Leone during the time the acts in the indictment were committed, the Court noted the Sierra Leone government made a statement in its 1996 Report to the Committee of the Rights of the Child that the minimum age for children conscripted into the army under the Geneva Conventions was fifteen. Therefore, the Court determined that NCSL was upheld because the government of Sierra Leone was fully aware during the time that the acts were alleged that children under the age of fifteen should not be recruited into the army.

More recently, the Extraordinary Chambers in the Courts of Cambodia (ECCC) weighed in on the application of NCSL in Case 002.  The tribunal said a crime charged at the ECCC must have existed at the time it was committed in national law, international law, or customary law. Case of IENG Sary, Decision on IENG Sary’s Appeal against the Closing Order, Apr. 11, 2011.  The Pre-Trial Chamber held that the Accused could be tried for the crimes of genocide and crimes against humanity because they were part of customary international law by 1975 and because Cambodia was bound by the Geneva Conventions, to which it was a party at the time, and was thus obligated not to commit grave breaches of that Convention. 

More recently, in September 2011, the Pre-Trial Chamber held in Case 002 that only specific modes of Joint Criminal Enterprise (JCE) existed in customary international law at the applicable time alleged in the Closing Order.  Case of IENG Sary, Decision on the Applicability of Joint Criminal Enterprise, Sept. 12, 2011.  The Pre-Trial Chamber ruled that while JCE I and JCE II liability would have been sufficiently accessible and foreseeable to the defendants in 1975, there was not sufficient evidence of consistent state practice involving the defendants regarding JCE III during the time they committed the alleged acts. The Chamber examined the Terrorist Bombing Convention and the Rome Statue of the ICC, sources used by the ICTY during the Tadić case to establish the legality of JCE III.  These two sources were not in existence during the time the alleged acts were committed in Cambodia from 1975 to 1979. Thus the Pre-trial Chamber was not “able to identify in the Cambodian law, applicable at the relevant time, any provision that could have been given notice to the Charged persons that such extended form of liability is punishable as well."  As a result, JCE as a mode of liability was limited due to NCSL.

The principle of NCSL is a fundamental right of an accused.  International criminal tribunals are often faced with challenges regarding compliance with NCSL and have subsequently shaped and defined NCSL in the context of international criminal law. Cases have upheld the importance of this principle and examined how to determine if a particular accused had knowledge of the law at the time of his alleged acts and if he reasonably believed his acts not to be criminal. By examining inter alia customary international law and existing treaties at the time of the alleged acts, tribunals can determine whether NCSL has been violated, helping to insure an accused’s right to a fair trial.