Reference re Assisted Human Reproduction Act is the Supreme Court of Canada’s most important ruling on the criminal law power in more than a decade. It demonstrates that the Court has become uncomfortable with the federal government’s use of section 91(27) of the Constitution Act, 1867 as Parliament’s general regulatory power. The paper begins with a review of the Assisted Human Reproduction Act, with particular reference to those aspects of the statute at issue in the Reference. Next, the three opinions delivered in the Reference are analyzed and their doctrinal significance identified. Finally, consideration is given to the implications for future federalism cases of the principles flowing from the Reference and how in its wake the regulation of health generally and of assisted reproduction technologies particularly should proceed. The author argues that the federalism principles emerging from the Reference are to be welcomed as they will assist in ensuring that the criminal law power does not become the source of wide-ranging civic regulation