Lawmakers interested in regulating in relation to environmental issues must bear in mind which aspects of the physical environment fall under federal jurisdiction, which are under provincial jurisdiction, and which may be regulated by both levels of government. In this paper, the word "regulate" is used in its generic sense, meaning control by coercion. It encompasses the enactment of legislation by Parliament or a provincial legislature and the making of regulations by a government, as well as government decision making and management of an issue when backed by the force of law. Sections 91 and 92 of the Constitution Act, 1867 list subject matters in relation to which each level of government may regulate. Neither list includes "environment" as a subject matter. Rather, the "environment" is a collective term referring to numerous issues, including some of the various subject matters the Constitution does assign to either Parliament or the provincial legislatures. This paper provides an introductory explanation regarding the constitutional basis for jurisdiction to regulate a subject matter, and then explains which level of government is responsible for regulating various environmental issues.