Trade bans are a good way to help protect endangered species. If the demand for animals who's very existence is threatened by such trade goes down, then we could work towards preserving the life of these animals. It is cruel and inhuman punishment that needs to be stopped, and banning the trade of these animals is a step in the right direction.
Yes, trade bans are a good idea for protecting endangered species, because banning a species in a country decreases demand for that species. If people cannot legally have something made from an animal, it will decrease the demand for harvesting the animal, because less people will want to buy the animal. With less demand, fewer poachers will want to kill the animal.