I'm not sure if I'm misunderstanding your comment, but killing animals for pleasure alone is already largely illegal in Western countries. And that includes hunting. You aren't allowed to just hunt an animal for fun and then leave it unharvested. It is hard to enforce, obviously. But you can definitely be charged for killing deer, moose, ducks, even fish, without a license and at least the intent to eat it. For example, you can't kill a bear, cut off its paws or gall bladder, and then throw the carcass in the bush. You also can be charged for killing or treating an animal inhumanely or in a way that causes it distress. That theoretically applies to all animals, including pets, livestock, aquariums, wildlife, and even small animals like mice and bats.