55 100. The Human Rights Committee has already recommended that domestic legislation be modified to protect the confidentiality of medical information.100 101. The Court considers that physicians have a right and an obligation to protect the confidentiality of the information to which, as physicians, they have access. 102. Consequently, in light of the above considerations, the Court believes that, when delivering the judgment of November 21, 1996, the State violated the principle of legality: by taking into account as elements that gave rise to criminal liability, membership in a terrorist organization and failure to comply with the reporting obligation, but only applying an article that did not define these behaviors; by not specifying which of the behaviors established in article 4 of Decree Law No. 25,475 had been committed by the alleged victim in order to be found guilty of the crime; for penalizing a medical activity, which is not only an essential lawful act, but which it is also the physician’s obligation to provide; and for imposing on physicians the obligation to report the possible criminal behavior of their patients, based on information obtained in the exercise of their profession. 103. In view of the above, the Court considers that the State violated the principle of legality established in Article 9 of the American Convention, to the detriment of Mrs. De La Cruz Flores. * * * 104. Likewise, for the sake of legal certainty, the punitive norm must exist and be known, or could be known before the occurrence of the act or omission that violates it, and which it is intended to penalize. 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. If this were not so, individuals would not be able to adjust their behavior according to the laws in force, which express social reproach and its consequences. These are the grounds for the principle of the non-retroactivity of an unfavorable punitive norm.101 105. According to the principle of freedom from ex post facto laws, the State may not exercise its punitive power by applying penal laws retroactively that increase sanctions, establish aggravating circumstances or create aggravated types of offenses. The principle is also designed to prevent a person being penalized for an act that, when committed, was not an offense or could not be punished or prosecuted.102 106. In relation to the principle of freedom from ex post facto laws, the Court observes that, in her statement of September 7, 1995, before DINCOTE, Elisa Mabel 100 Cf. Final observations of the Human Rights Committee, Chile, U.N.Doc.CCPR/C/79/Add.104 (1999). 101 Cf. Case of Baena Ricardo et al., supra note 97, para. 106; and, inter alia, Eur. Court H.R. Ezelin judgment of 26 April 1991, Series A no. 202, para. 45; and Eur. Court H.R. Müller and Others, judgment of 24 May 1988, Series A no. 133, para. 29. 102 Cf. Case of Ricardo Canese, supra note 1, para. 175; and Case of Baena Ricardo et al., supra note 97, para. 106.