THE PRINCIPLE OF LEGALITY: NULLUM CRIMEN SINE LEGE

Article 9 of the American Convention enshrines a basic principle of criminal law the Latin wording of which is nullum crimen et nulla poena sine lege. This constitutes “the principle of legality” explained by the Court in Berenson as follows: “The definition of an act as an unlawful act and the determination of its legal effects must precede the conduct of the individual who is alleged to have violated it; because, before a behavior is defined as a crime, it is not unlawful for penal effects”. It is a fundamentally important principle for the protection of several human rights, leading the Convention to establish it as an international State obligation that cannot be suspended, even in an emergency situation. This provision also enshrines the principle that a convict must receive a lesser punishment when a lesser punishment is established by law after the commission of a crime.

Like Article 8, Article 9 of the Convention applies to all criminal convictions, regardless of significance or scope. However, it does not apply to procedural law, because that law applies at the moment a procedural act is carried out, independently of the date of the commission of the offense. In the case of Liakat Alit Alibut, the Court relied heavily on case law of Latin American States and of the European Court.