Good luck enforcing the ban without war.
I guess, if the world would come together each time to help the stronger war party, the wars would be over more quickly. And, unless the aggressor's goal is decimation, this way the wars would cost fewer lives.
But then the stronger party would start more wars, maybe ? So more shorter wars ?
Anyway, we are already doing this. Stronger parties get away with much expoils just for fear by others that they start a war. Wars don't get shorter than submission before they start. And that's a daily commonplace thing.
We could also ban weapons manufacturing, armies, etc. And jail more warmongering overlords. The question is how.
Not forgetting the 70.000.000.000 chickens killed each year by humans for consumption, which I think is the most popular bird so this amount isn't the total amount of birds killed.
Wow. That's worlwide, I hope. Still 9 whole chickens per person per year is a lot. If at least that was the only meat people eat, but there're many more.
I think people should eat less meat, ideally none, but anyway, I'm more worried by accidental deaths than killing to feed other animals. Animals are living beings that kill other living beings to survive (that's not exact, frugivors can eat just part of plants without killing them, mosquitoes do kill a lot but they don't need to for survival, is more like a side job of transporting pathogens). Vegetables survive without killing anyone. So killing an animal is kind of more just than killing a vegetable (at least in a Talion, Hammurabi, or tit for tat way). But raising an animal kills more vegetables than eating vegetables, so eat vegetables, no matter it's individually more unjust.
But killing a living being and not even eating it, that's lame (unless self defense, did you hear mosquitoes?).