Legal paternalism occurs when the law forces individuals to avoid certain risks (‘hard paternalism’), or, without coercion, nudges them away from such risks (‘soft paternalism’), on the ground that otherwise they will make unwise decisions. The questions when and how such approaches should be taken are of fundamental importance in a society in which there are increasing risks to health and livelihood resulting from technological developments and greater freedom of choice. However, they are not openly addressed in policy-making circles and have also been neglected in the European legal literature. In this paper, I attempt to explain these paradoxes and to outline a theoretical benefit–cost framework for determining when and how legal paternalism might be considered appropriate.