So IOW it was all about taxation to the Canadian authorities? No concern about an illegal border crossing?
The taxes were probably a main thing, but probably also an illegal border crossing as well (that issue or concern probably not on the same sort of scale as it is nowadays).
I told my mother this story soon after and she remarked about how that probably was not the first time that that farmer saw people trying to sneak booze across his property.
Drinking age is 18 in Quebec—19 in most of the rest of Canada. One may import a certain amount without paying duty (in this case it would be U.S. duty) if one has been out of the country for 48 hours.