Reference Re Validity of Section 5(a) of the Dairy Industry Act (1949), also known as the Margarine Reference or as Canadian Federation of Agriculture v Quebec (AG),[1] is a leading ruling of the Supreme Court of Canada, upheld on appeal to the Judicial Committee of the Privy Council, on determining if a law is within the authority of the Parliament of Canada's powers relating to criminal law.

"[8] If true, that would have made margarine a fair target for criminal law, but the federal government admitted before the courts that the assessment was simply false.

[9] The Court ruled: Rand J, in his concurring opinion for the majority, struck down the prohibition on production of margarine on the grounds that it was not valid criminal law.

The ruling was appealed to the Privy Council, on the grounds that the legislation was valid under the following: The Supreme Court ruling was upheld by the Board, which responded to the points appealed thus: The public interest in this regulation lies obviously in the trade effects: it is annexed to the legislative subject matter and follows the latter in its allocation to the one or other legislature.

But to use it as a support for the legislation in the aspect of criminal law would mean that the Dominion under its authority in that field, by forbidding the manufacture or sale of particular products, could, in what it considered a sound trade policy, not only interdict a substantial part of the economic life of one section of Canada but do so for the benefit of that of another.