The Double Aspect doctrine is a tool of constitutional interpretation used when both levels of government have an equally valid constitutional right to legislate on a specific issue or matter. Double Aspect represents the modern notion of co-operative federalism, which abandons the out-dated idea that every subject matter falls under the exclusive control of either the federal or provincial government.

Double Aspect fosters respect for the decisions of the elected legislatures of both levels of government. As the name indicates, the double aspect doctrine acknowledges that both Parliament and the provincial legislatures can pass valid legislation relating to the same subject depending on the aspect from which the subject is being approached.

The best example of this doctrine at work is in Multiple Access v McCutcheon, a 1982 case that dealt with insider trading in Ontario. Both levels of government passed legislation to combat insider trading: the Federal government passed legislation dealing with federally regulated corporations, while Ontario’s legislation focussed on the actual acts of insider trading. The Provinces could claim the power to do this through their constitutional powers over property and civil rights, which includes securities trading such as what was occurring in this case. The Federal government had an equally strong jurisdictional claim through its ability to regulate for the peace, order and good government of Canada. The Supreme Court ruled that both pieces of legislation were valid because they dealt with different aspects of the same problem that fell within the constitutional powers of the enacting legislature.

Prominent Double Aspect Cases:

Multiple Access v McCutcheon