In Islamic law paternity is treated as a consequence of a licit sexual relationship. Since DNA testing makes a clear distinction between legal and biological paternity possible, it challenges the continued correlation between paternity and marriage. This article explores the foundations of paternity regulations in the Islamic ethico-legal tradition, with a particular focus on what is termed here “the licit sex principle,” and investigates the extent to which a harm-based argument can be made either by appeal to or against Islamic (...) paternity regulations. It argues that in Islamic bioethics the definition of harm and its boundaries is a function of both: (1) identification of legal and religious rights and the extent to which these rights are violated; and (2) balancing and reconciling perceived harm against both specific principles in relation to a given issue and also the overarching objectives of Islamic law. The article is divided into three main sections addressing the Islamic legal, ethical, and bioethical dimensions of paternity. (shrink)