Some nature reserves have to cull some of their animals and will sell the meat to food suppliers and restaurants. It's not endangered animals' meat, because they don't cull those, but it is unusual and exotic, things like gazelle, zebra, crocodile etc sourced from Africa and sold in Europe or America. Could call it ethical depending on your particular morals, since they have to be killed anyway for environmental reasons so it's not as if they're being farmed specifically to be killed.