82 171. Article 9 of the American Convention establishes that: No one shall be convicted of any act or omission that did not constitute a criminal offense, under the applicable law, at the time it was committed. A heavier penalty shall not be imposed than the one that was applicable at the time the criminal offense was committed. If subsequent to the commission of the offense the law provides for the imposition of a lighter punishment, the guilty person shall benefit therefrom. 172. In the instant case, the Commission and the representatives argued that Paraguay did not apply to Canese the most favorable norm that entered into effect on November 26, 1998, after the judgment of second instance convicting him had been handed down on November 4, 1997. The State indicated that it had not violated the principles of legality and retroactivity and that Ricardo Canese was absolved by the application of the most favorable penal norm in the judgment delivered by the Supreme Court of Justice of Paraguay on December 11, 2002. 173. In order to consider the alleged violation of Article 9 of the Convention in this case, it is necessary to refer to the principles of legality, non-retroactivity of the unfavorable norm, and retroactivity of the most favorable penal norm, which it is alleged was violated in the instant case. 174. Concerning the principle of legality in the penal sphere, the Court has indicated that the elaboration of penal categories presumes a clear definition of the criminalized conduct, which establishes its elements, and allows it to be distinguished from behaviors that are either not punishable or punishable but not with imprisonment. Ambiguity in describing offenses creates doubts and the opportunity for abuse of power, which is particularly undesirable when determining the criminal liability of an individual and punishing the latter with penalties that severely affect fundamental attributes such as life or freedom.150 175. According to the principle of the non-retroactivity of the unfavorable penal norm, the State is prevented from exercising its punitive power in the sense of applying retroactively penal laws that increase sanctions, establish aggravating circumstances or create aggravated types of offenses. It is also designed to prevent a person being penalized for an act that, when it was committed, was not an offense or could not be punished or prosecuted.151 176. This Court has interpreted that the principles of legality and non-retroactivity of the unfavorable norm are applicable not only in the penal sphere, but also, their scope extends to matters relating to administrative sanctions.152 177. Under the rule of law, the principles of legality and non-retroactivity govern the actions of all bodies of the State in their respective fields, particularly when the exercise of its punitive power is at issue.153 150 Cf. Case of Baena-Ricardo et al., supra note 139, paras. 108 and 115; Case of CantoralBenavides, supra note 139, para. 157; and Case of Castillo-Petruzzi et al., supra note 139, para. 121. 151 Cf. Case of Baena-Ricardo et al., supra note 139, para. 106; and Case of Castillo-Petruzzi et al., supra note 139, para. 120. 152 Cf. Case of Baena-Ricardo et al., supra note 139, para. 106. 153 Cf. Case of Baena-Ricardo et al., supra note 139, para. 107.