'What sort of conduct may the state legitimately make criminal?' This book compares the civil and common law approach to analyze this question. Siting the study within the Australian and German context, the book contrasts the Australian system with the German model based on "Rechtsgutstheorie". Supported by interviews with Australian criminal law experts, the work contrasts the largely descriptive, criminology- based Australian approach with the more sophisticated German model which is driven by legal theory which in turn has influenced the development of the criminal law. The hypothesis is framed that, as a result, the Australian approach suffers from a 'normative flaw', which is illustrated by comparing the different approaches to the offences of incest, bestiality and possession of illicit drugs. It is ultimately contended that, while there is strength in the Common law approach of describing the possible reasons for criminalising certain conduct, the approach could be significantly improved by scrutinizing the legitimacy of those reasons. The author argues that this could in turn develop into a normative concept to identify the 'good reasons' for criminalisation.