The contributions gathered in this special issue of Politix underline the interest of the notion of "differential management of illegal practices" formulated by Michel Foucault thirty years ago. The use of this notion in social sciences should be seen here as a contribution to government studies: in a context of tightening state control over certain populations, it focuses on the unequal enforcement of legal provisions by state agents in charge of qualifying and repressing illegality, without limiting the scope to the mere analysis of judicial actors. Studying the differential enforcement of the law first supposes analyzing the dispositions and the professional ethos of civil servants. But it also implies seeing the management of illegality as a collective and relational phenomenon: state officials act out in local arenas where other actors are able to use the law and negotiate its implementation. In the same way, this study requires thinking of the management of illegality and illegal practices themselves as mutually constitutive, and analyzing them jointly.