Ontario (AG) v Canada Temperance Federation[1] was a famous Canadian constitutional decision of the Judicial Committee of the Privy Council and was among the first cases to examine the peace, order, and good government power of the Constitution Act, 1867.

It was the first decision to bring back the "national concerns" branch of peace, order and good government since it was first suggested in the Local Prohibitions case.

In June 1939, the Ontario government posed the following reference question to the Court of Appeal of Ontario: Are Parts I, II and III of the Canada Temperance Act[2] constitutionally valid in whole or in part, and if in part, in what respect?In presenting its case, Ontario argued: In September 1939, the majority of the Court of Appeal (Riddell, Fisher, McTague and Gillanders JJA) gave the following answer: This Court is of opinion (Mr Justice Henderson dissenting) that Parts I, II and III of the Canada Temperance Act... are within the legislative competence of the Parliament of Canada.Ontario appealed the ruling to the Privy Council.

As to the arguments raised by Ontario, Viscount Simon for the Council also suggested that the federal power relating to peace, order and good government could be invoked for matters of "national concern:" In their Lordships' opinion, the true test must be found in the real subject matter of the legislation: if it is such that it goes beyond local or provincial concern or interests and must from its inherent nature be the concern of the Dominion as a whole (as, for example, in the Aeronautics case and the Radio case), then it will fall within the competence of the Dominion Parliament as a matter affecting the peace, order and good government of Canada, though it may in another aspect touch on matters specially reserved to the provincial legislatures.

Many decisions to follow struggled to reconcile the case with that of Russell and seem to give contradictory interpretations of the nature of "peace, order and good government."