The present study aims to understand the legal and political contours of truth commissions, in order to examine the promises, the potentialities and the limits of this mechanism of transitional justice. The broadest goal of this work is to situate truth commissions within contemporary relationships stablished between truth, law and memory. It seeks to critically reflect about the ways in which these new mechanisms of justice affect our way of naming and understanding forms of violence (especially state-sponsored violence). The central hypothesis holds that the regime of truth-making within truth commissions — in its complex, contradictory and ambiguous relationship with law, history, and memory — maintains an inseparable link with the process of official writing of violence (its outlines, gaps and silences). Indeed, far from constituting a neutral or finished solution for the legacies of grave human rights violations, truth commissions are, above all, a space of conflict between different memories and a space of dispute of the meanings granted to the past of violence. The experience of the Brazilian National Truth Commission is finally addressed as a reference for the study of truth commissions (and more broadly for the study of transitional justice), capable of bringing relevant contributions to the analysis of these mechanisms of justice.