In October 1792, the Convention began its works in the lawsuit of Louis XVI: the young Saint-Just had the task of supporting the thesis of eligibility and condemnation of the king. The Convention is deeply divided and it seems initially dominated by Morisson’s position which upholds the impossibility of the procedure due to the absence of an appropriate law: “nulla poena sine lege”. Saint-Just recurs at the Ciceronian thought to transfer the question from the positive law (recognizing the principle of non-retroactivity) to jus gentium; on this basis, the entire Ciceronian dossier on the "revolutionary" in the late Republic becomes the precondition that allows Saint-Just to conceptualize more geometrico the accusation to the king. One Rhetorical tool among the many used is that of Metabolēs organized within the tripartite classical in inventio, dispositio ed elocutio, enlivened by the imitatio and convenientia. Borrowing from Cicero the legal lieux spécifiques, by the use of anaphora highlighted through a perfect rhythmic symmetry, Saint-Just manages to persuade the audience that Louis is not only a traitor to the State even before the nation, but also a barbarian, and then a foreigner, so that his death sentence appears as the only acceptable solution.
