I begin with the origins of reciprocity, since this motivational force takes a central position in my political economy of behavioural public policy. The behavioural influences that tend to be labelled as errors by most behavioural economists, and as such have served as the justification for a paternalistic direction in behavioural public policy, in an ecological sense may not be errors at all. We thus cannot conclude that attempts to modify people’s choices in accordance with these so-called errors will improve the lives of those targeted for behaviour change. Where people are imposing no substantive harms on others, policy makers should restrict themselves to protecting and fostering reciprocity, which benefits the group and most of the people who comprise it, irrespective of their own personal desires in life. However, when one party to an exchange uses the behavioural affects to benefit themselves but imposes harms on the other party, the concept of a free and fair reciprocal exchange has been violated. I thus argue that there is an intellectual justification to introduce behavioural-informed regulations against activities that impose unacceptable harms on others.