Sunstein and Thaler’s ‘libertarian paternalism’ (LP) is inspired by the findings of behavioural economics. Its ambitious policy agenda promotes interference which does not block free choice when agents fall short of fully informed and rational choice. Their implicit version of the informed desire view of welfare either provides no, or potentially erroneous, guidance to planners. LP thus faces significant implementation problems. To address these LP might adopt a weaker version of the information requirement on desires or an alternative view of welfare. Nonetheless, informational and bounded rationality considerations suggest that LP should be rethought and its level of ambition reduced.