Unfortunately, I am not in a position to explain the minister's reasoning. I can however say that one of the reasons why the constitutionality of the Quebec law raises questions is the fact that the issue is a matter of shared jurisdiction, and criminal law is of exclusive federal jurisdiction.
The Quebec law says that whoever acts pursuant to section 26 of the law is not guilty of a criminal offence. A court might decide that this is a matter of criminal law and that the provinces and territories do not have the jurisdiction to determine in which circumstances a given act is criminal or not. So there is a constitutional issue. That is all I can say about that.