This paper analyses the aesthetics codes and cultural symbols attached to the official commemoration of slavery in Nantes, held annually in May 10, and highlights how they frame the interpretation of slavery and its legacy according to the traditional “republican” vision of collective identities. Such vision has recently been challenged by actors from Nantes' black community who have organized a theatrical “re-enactment” of slavery, with costumes and masks, designed to highlight the violence exerted on slaves. The strong contrast between these two modes of memorialization reflects two competing political uses of the past, related to two kinds of ideological worldviews. The first one tries to integrate the slave-trade past in the patrimony of the political body, an operation that requires to downplay contentious dimensions such as racial prejudice, culpability and debt. Through “real” representation and alternative cultural references (such as the American civil rights movement), the other form of commemoration supports a more contentious approach of the slavery legacies, one that puts racial identities and contemporary inequalities at the foreground. Relying on extensive fieldwork observations and interviews, the case explored in this paper provides a detailed vision of the social processes that makes the commemoration of the past a resource to consolidate the political order, or to challenge it.