13 punitive power is at issue. In a democratic system, precautions must be strengthened to ensure that punitive measures are adopted with absolute respect for the basic rights of the individual, and subject to careful verification of whether or not unlawful behavior exists. In this regard, when applying criminal legislation, the judge of the criminal court is obliged to adhere strictly to its provisions and observe the greatest rigor to ensure that the behavior of the defendant corresponds to a specific category of crime, so that he does not punish acts that are not punishable by law.22 44. Based on the foregoing, the IACHR will analyze whether the Argentine State, in the verdict of the Appeals Chamber that convicted Mr. Mohamed, complied with the principles of legality and non-retroactivity of criminal law, recognized by Article 9 of the Convention. 45. The principle of non-retroactivity established in Article 9 of the American Convention embraces the basic principles of nullum crimen sine lege and nulla poena sine lege, which prohibit states from prosecuting or punishing persons for acts or omissions that did not constitute criminal offenses, under applicable law, at the time they were committed.23 As interAmerican jurisprudence has interpreted,24 this principle requires states to classify and describe crimes in precise and unambiguous language that narrowly defines the punishable offense, establishing its elements and the factors that distinguish it from behaviors that are either not punishable offenses or are punishable by other penalties,25 in order to clearly define what conduct people must refrain from.26 The IACHR has established that “The principle of legality has a specific role in the definition of crimes; on the one hand, it guarantees individual liberty 1022 Inter-American Court, Case of de la Cruz Flores v. Peru, Judgment of November 18, 2004 (merits, reparations, and costs) Series C. No. 115, paras. 80, 81, and 82. 1123 IACHR, Report on Terrorism and Human Rights, OEA/SER.L/V/II.116, Doc 5 Rev. 1, corr., October 22, 2002, para. 225. 1224 I/A Court H. R., Case of Castillo Petruzzi et al, Judgment of May 30, 1999 (merits, reparations, and costs), Series C No 52; IACHR, Report on the Human Rights Situation in Peru (2000), OEA/Ser.L./V/II.106, Doc.59 rev. 2, June 2, 2000, paras. 80 and 168; IACHR, Report on Terrorism and Human Rights, OEA/SER.L/V/II.116, Doc 5 Rev. 1, corr., October 22, 2002, para. 225. 25 I/A Court H. R.,, Case of De La Cruz Flores v. Peru, Judgment of November 18, 2004 (merits, reparations, and costs) Series C. No. 115, para. 79: “Concerning the principle of legality in the penal sphere, the Court has indicated that the elaboration of criminal categories involves a clear definition of the criminalized conduct, establishing its elements, and the factors that distinguish it from behaviors that are either not punishable or punishable but not with imprisonment.” See also: I/A Court H. R.,, Case of Ricardo Canese v. Paraguay. Judgment of August 31, 2004. Series C No. 111, para. 174; I I/A Court H. R., Caso of Castillo Petruzzi et al. v. Peru. Preliminary Objections. Judgment of September 4, 1998. Series C No. 41, para.121; I/A Court H. R., Caso of Cantoral Benavides v. Peru. Judgment of August 18, 2000. Series C No. 69, para. 157. 026 IACHR. Report on Terrorism and Human Rights, OEA/SER.L/V/II.116, Doc 5 Rev. 1, corr., October 22, 2002, para. 17.