One difficulty in dealing with the concept of medical treatment in Canadian criminal law is to reconcile some of the dictates of the Criminal Code, which have ancient origins, with the reality of modern medicine. Such a situation arises when we ask whether a surgical operation is prima facie legal or illegal. This may be considered a rather narrow and esoteric question, but it has and will become increasingly important with the development of modern medical technology. The initial presumption of legality or illegality may determine the final characterization of a given medical intervention as lawful or unlawful. This is particularly important in such areas as non-therapeutic human medical research and live-donor organ transplantation. This enquiry explores the present situation in Canadian criminal law with respect to the legality of medical interventions and makes some recommendations for change.