The work develops an analysis of Sunstein’s libertarian paternalism and his critique of Mill’s Harm Principle. It compares three standpoints: (A) the antipaternalism of Mill’s Harm Principle, (B) Sunstein’s libertarian paternalism, and (C) the nonlibertarian paternalism typically exemplified by legal prohibitions. The work claims that, with some qualifications, (B) is compatible with (A), since libertarian paternalism does not generate the obligations or prohibitions that the Harm Principle disqualifies. At the same time, the work points out some problems and ambiguities that affect Sunstein’s arguments, notably the creation of duties for the purpose of nudging (e.g. duties on producers to benefit consumers) and the extension of nudges to conduct that is legally obligatory (e.g. paying taxes).