Watertight Compartments: Getting Back to the Constitutional Division of Powers

This article offers a fresh examination of the constitutional division of powers. The author argues that sections 91 and 92 of the Constitution Act, 1867 establish exclusive jurisdictional spheres — what the Privy Council once termed “watertight compartments.” This mutual exclusivity is emphasized and reinforced throughout these sections and leaves very little room for legitimate overlap. While some degree of overlap is permissible under this scheme — particularly incidental effects, genuine double aspects, and limited ancillary powers — overlap must be constrained in a principled fashion to comply with the exclusivity principle. The modern trend toward flexibility and freer overlap is contrary to the constitutional text. The author argues that while some deviation from the text is inevitable due to the presumption of constitutionality and stare decisis, the Supreme Court should return to a more exclusivist footing in accordance with the text.