This article explores the transitional justice (TJ) dilemmas after revolutions have overthrown autocratic regimes through developing a model that uses a law and economics methodology. The article seeks to answer two questions: Why do post-revolution regimes resort to or ignore TJ policies towards former autocratic regimes? And why is it difficult to adopt and apply welfare-enhancing TJ mechanisms in practice, including popular suggestions within the TJ literature to portray the civil society organizations as the key solution to TJ dilemmas? To answer these questions, the article provides a theoretical positive analysis of the scenarios and dilemmas of TJ. It argues that TJ should function both as an internalization mechanism of negative externalities of the violations of the past-regime, and a form of constitutional arrangements as an ex ante incentives structure to prevent the repetition of these violations. However, due to asymmetric information problems, behavioural biases and the constitutional nature of TJ, the ‘TJ momentum’ precludes most of the traditional solutions for this principal–agent problem.