This paper reconstructs Foucault's concept of illegalism and explores its significance for his genealogies of modern punishment and racial formation. The concept of illegalism, as distinct from illegality, plays a double role. It allows Foucault to describe a ruling class tactic for managing inequalities and also to characterize an important vein of resistant subjugated knowledges. The political project of the prison is linked to a new crime policy that does not so much aim to repress illegalisms as to manage them differentially. This practice of differential management, which arises in the 18th century, produces a primary split along class lines between two types of illegalism—an insight that has a certain resonance with Edwin's Sutherland's concept of “white collar crime.” Foucault's investigation of a third category of “infralegal illegalism” sheds light not only on the genealogy of the category of delinquency but also on his genealogy of racial categorization. Finally, Foucault argues that a genuinely radical critique of modern society must address the “need” organized political power has for the illegalisms from which it purportedly seeks to protect society. Against this practice of differentially managing illegalisms, Foucault seeks to reactivate a subjugated problematic that might open up questions about the transformative possibilities of illegalism today.