How can we explain that judges’ criticisms do not transform the practices of their own court? According to the actors of the International Criminal Court, it is a matter of legal culture. Because of the domination of common law, judges cannot control the prosecution policy, which relies on the will of international diplomacy and established powers. While describing and understanding this explanation, the author enquires about legal cultures in action. He shows how they interact with the call for the rationalization of justice and he concludes that the jurisdiction’s institutional weakness makes the force of law it produces and undermines the possibility for judges to publicize their criticisms, which could endanger the Court’s façade of unity.