Due to an oversight on my part, my forthcoming article Canadian Blasphemy Law in Context: Press, Legislative, and Public Reactions doesn't include anything about an interesting little document I dug up in the archives a couple of years ago. The 1955 document is a two-page memorandum of a discussion within the Canadian Privy Council Office (Federal cabinet ministers) about a recent (1954) act of the Quebec legislature which prohibited "the making of abusive or insulting attacks against the practice of a religious profession or the religious beliefs of any portion of the population of the province." The Minister of Justice advised that the Act overlapped with the Criminal Code's prohibition on blasphemous libel and thus created confusion, and that perhaps both the federal and the provincial law should be sent to the Supreme Court of Canada as a reference question to determine their validity. The idea was shot down, however, because challenging Quebec legislation would make the Federal government unpopular in the province and a Federal-Provincial Conference was coming up shortly.
Such a reference, had it been made, may or may not have resulted in the Supreme Court holding that the Quebec act was ultra vires or preempted, but the Federal Criminal Code provision would presumably be on solid ground since it would fall squarely within the criminal law making power attributed to the Federal government (and neither the statutory Bill of Rights or the constitutional Charter of Rights and Freedoms had been enacted at that time in Canada).
A scan of the document, with the citation written at the top, is included below.