Launching a protest movement implies the establishment of a self-categorisation that sets forth the terms of its membership and its political aims from within. Claiming all members’ right to collective legalisation, immigrants without residence/working permits have constituted the “sans-papiers”/“undocumented” category to counter other-categorisations, such as “illegal immigrants” and “clandestine”, which associate the designated population with illegality, and to apply pressure for political change. This paper offers detailed analyses of the ways members of a protest movement (2001, Fribourg, Switzerland) established and used the “sans-papiers” category as official speakers during press conferences. It shows on the one hand speakers’ ingenious in situ deployment of resources offered by the press conference format for doing protest. On the other hand, it reveals speakers’ transforming categorial work that indexes inherent tensions that the setting-up of a “revolutionary category” might imply for its members when confronted to politico-institutional challenges engendered by their protest.