35 113. As for the principle of freedom from ex post facto law, contained in Article 9 of the American Convention, the Inter-American Court has held that: [C]rimes must be classified and described in precise and unambiguous language that narrowly defines the punishable offense, thus giving full meaning to the principle of nullum crimen nulla poena sine lege praevia in criminal law. This means a clear definition of the criminalized conduct, establishing its elements and the factors that distinguish it from behaviors that are either not punishable offences or are punishable but not with imprisonment. Ambiguity in describing crimes creates doubts and the opportunity for abuse of power, particularly when it comes to ascertaining the criminal responsibility of individuals and punishing their criminal behavior with penalties that exact their toll on the things that are most precious, such as life and liberty. 93 [U]nder the rule of law, the principles of legality and non-retroactivity govern the actions of all bodies of the State in their respective fields of competence, particularly when the exercise of that punitive power is at stake. 94 In a democratic system it is necessary to intensify precautions in order for such measures to be adopted with absolute respect for the basic rights of individuals, and subject to a careful verification of whether or not there was unlawful conduct. 95 114. The petitioners contend that one of the fundamental pieces of the so-called “zero tolerance” policy was amendment of Article 332 of the Penal Code, which criminalizes unlawful association. This amendment was done with passage of the so-called “Anti-Gang Act”, which increased the sentences for this crime. The language of the description of the crime made specific mention of “gangs” as a form of unlawful association. 115. The National Congress approved this amendment on August 7, 2003, by Decree No. 117-2003; the amendment took effect on August 15. That pertinent part of that decree reads as follows: THE NATIONAL CONGRESS […] HEREBY DECREES: ARTICLE 1. To amend Article 332 of the Penal Code, contained in Decree No. 144-83 of August 23, 1983, to read as follows: ARTICLE 331. UNLAWFUL ASSOCIATION. Heads or leaders of gangs and other groups that exist for the purpose of committing any act constituting a crime shall face a sentence of nine (9) to twelve (12) years imprisonment and a fine of ten thousand (L. 10,000) to two hundred thousand (L. 200,000) lempiras. Members of those unlawful associations shall also face the same sentence, reduced by one third (1/3). Heads or leaders are those persons who stand out or identify themselves as such and whose decisions influence the group’s state of mind and actions. 96 I/A Court H.R., Case of Castillo Petruzzi et al. v. Peru. Judgment of May 30, 1999. Series C No. 52, paragraph 121; I/A Court H.R., Case of De la Cruz Flores v. Peru. Judgment of November 18, 2004. Series C No. 115, paragraph 79. 93 94 I/A Court H.R., Case of Baena Ricardo et al. v. Panama. Judgment of February 2, 2001. Series C No. 72, paragraph 107; I/A Court H.R., Case of Ricardo Canese v. Paraguay. Judgment of August 31, 2004. Series C No. 111, paragraph 177; I/A Court H.R., Case of De la Cruz Flores v. Peru. Judgment of November 18, 2004. Series C No. 115, paragraph 80. 95 I/A Court H.R., Case of Baena Ricardo et al. v. Panama. Judgment of February 2, 2001. Series C No. 72, paragraph 106; Case of De la Cruz Flores v. Peru. Judgment of November 18, 2004. Series C No. 115, paragraph 81. The petitioners’ observations on the merits, dated April 10, 2009. Annex 13. La Gaceta, Friday, August 15, 2003. No. 30,163. 96