The truth is that at the border, the Canadians ask you if you are bringing wine, etc into Canada, which I have found weird.
But then, on the way back, the USholes also ask if you are bringing food from Canada in.
That should stop. There is so much great stuff to eat in Montreal, that you cannot find here, that is mind boggling. You go into a food market, supermarket, etc. there, and there is stuff that will blow the mind of people in US supermarkets, but it is not available here.
So, it takes two to tango, and this dairy stuff is just a canard.