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ALLEGED VIOLATION OF PRINCIPLE OF LEGALITY (ARTICLE 9, FREEDOM FROM
EX POST FACTO LAWS), IN RELATION TO THE OBLIGATION TO RESPECT AND
GUARANTEE RIGHTS
A) Arguments of the Commission and of the parties
128. The Commission indicated that in this case the judgment of the Chamber of
Appeals in which Mr. Mohamed was convicted, “integrated the crime of manslaughter
established in Article 84 of the [Argentine] Criminal Code, with the provisions of Decree
No. 692/92.” The Commission argued that this regulation entered into force on April 27,
1992, while the events of the present case took place on March 16 of the same year,
thereby violating the principle of legality, enshrined in Article 9 (Freedom from Ex Post
Facto Laws) of the American Convention. Furthermore, it pointed out that said violation
“was not remed[ied] by the judgment of the Chamber of Appeals that declared
inadmissible the special appeal”, because the ruling of the Appeals Court “eliminated the
[r]egulations not in effect and determined that, in any case, Mr. Mohamed had breached
his duty of care.” For the Commission, this action by the Chamber of Appeals resulted in
a new violation of the principle of legality with respect to the precise definition of
criminal offenses.
129. The representatives pointed out that in this case the principle of legality was
violated because the conviction was based on a regulation that was not in effect, given
that, at the time of the events, Decree No. 12.689, issued in 1945, was in force. The
representatives further stated that, on the sole basis of Article 84 of the Argentine
Criminal Code, no one would be able to assess the prohibited actions, since “[o]nly when
the prohibitions or mandate are known and comprehended (for which, the regulations
must precede the acts being tried), may acts or omissions in breach of the duty of care
be criminally enforced.” In addition, they indicated that the “act attributed” to Mr.
Mohamed “was (and is), not only punishable by prison sentence, but mandatory
disqualification,” which only applies to regulated conduct.” They further argued that, for
this reason, the application of the disqualification “must necessarily be based on the
violation of a regulation or law that regulates the activity in the context in which it takes
place.” The representatives also referred to the danger of infringing the principle of
criminal legality entailed in negligent criminal offenses and argued that, in these cases, it
is necessary to increase precautions so as not to violate the already jeopardized principle
of legality. In addition, they pointed out that “the text of Decree Nº 12689/45 is
markedly different from Decree 692/92” and that even the aforementioned Decree of
1945 “impeded any possibility of a criminal conviction against Mr. Mohamed.” As to the
retroactivity of the lighter penalty, the representatives noted that it is irrelevant that the
American Convention refers only to the non-retroactivity of the “crime and not the
punishment”, since there is no crime without punishment.
130. The State argued that when dealing with cases of offenses of negligence, it is not
possible to identify the prohibited conduct without referring to another regulation that
indicates the duty of care, and that even though “[o]ften, the objective duty of care is
established by law, […] no regulation exhausts all of the possible forms of violation of
the duty of care that may arise” and, for this reason, “it always refers to a general
formula” that deals with “social patterns of care.” Regarding the alleged application in
the case of Mr. Mohamed of a regulation that was not yet in force, Argentina noted that
“to the extent that the sentence describes the negligent or reckless conduct used to
establish the elements of the crime, the mere mention of a regulation not in effect at the
time of the facts does not constitute a violation of the principle of legality, so long as
these classifications were set out in a regulation which was itself in effect.” In addition,
Argentina stressed that the operative part of the conviction of the Chamber of Appeals,
dated February 22, 1995, “mentions as the criminal law violated and legal source of the
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