The act of iudicare hostes (‘declare public enemy’) was a formal pronouncement of the Roman Senate, voted for the first time in 88 BCE following a proposal by L. Cornelius Sulla after his first march on Rome. Legal historians have generally interpreted it as an emergency measure intended to preserve legality in a situation of civil strife and viewed it as a consistently defined institutional framework throughout the final decades of the Republic. Through an analysis of Sulla’s performative political communication, (...) before, during and in the immediate aftermath of the march, this paper argues that the act of judging (iudicare) someone a public enemy (hostis publicus) was first deployed as a political action, void of legal effects. Later instances of iudicare suggest that this act underwent a process of institutionalization after 63 BCE. (shrink)