I would say precedent had already been made. What basis were the VietNam dodgers allowed to stay?
Because they were "drafted" rather than enlisted?
If this is the case, this guy of his own volition signed on to military duty. He did not complete his enlistment obligation and he should be made to return to the U.S. to face charges according to the laws under which he enlisted.
Otherwise he is a liar and Canada is abetting a liar through their legal system.
This isn't refuge, or CO status at all.
Vietnam era draft resisters were allowed to stay because Canada considered draft evasion to be a civil affair, not a crime.
This guy is not a "resister" in any legal way, he is a deserter from the American Military and as such, is liable to criminal punishment.