Abstract
This article considers how legislators should respond to evidence that identifies a common and widely accepted parental practice as a potential source of harm to children, using domestic exposure to environmental tobacco smoke as a test case. It is claimed that children are parties to the Harm Principle, and that the State has an obligation to protect children from exposure to harm. Parental prerogative is limited by the need to avoid harming children. That said, there is considerable uncertainty about what is harmful to children. Several sources of uncertainty, both empirical and conceptual, are explored, in order to demonstrate the complexity of the task legislators face. Seven considerations that are relevant to decisions about legislation of harmful parental practices are outlined, and these considerations are then employed to assess the case in favour of legislating to prohibit the exposure of children to environmental tobacco smoke in domestic settings