In the Margarine Reference 1951, why was the federal law prohibiting margarine sales struck down?

The decision in the Margarine Reference (1951) highlighted the balance of powers between federal and provincial jurisdictions in Canada. The federal law prohibiting the sale of margarine was struck down because it was found to be a matter that fell under provincial jurisdiction, specifically concerning civil property rights and the ability of provinces to regulate products that were sold within their boundaries.

In this case, the Supreme Court of Canada determined that the regulation of food products like margarine was tied to provincial interests and the general welfare of the provinces, including the ability to control trade and commerce within their territories. This reflects the division of powers outlined in the Constitution Act, 1867, where provinces have the authority over local matters that do not extend into national interests.

The rationale used by the court emphasized that the federal government had overstepped its boundaries by encroaching on an area that was primarily the responsibility of the provinces. This illustrates how carefully delineated the responsibilities are between federal and provincial governments, reinforcing the need for federal legislation to remain within its constitutionally defined scope.