regardless whether it is a PED or not, its is a "banned" substance, there are rules in this sport, respect them
Dope may increase pain threshold and possibly stamina but there's no way it could be classified as performance enhancing. There are too many downsides although I have no direct experience boxing whilst under the influence. Is alcohol on the banned list of substances?
PS Arreola has clearly had issues with the munchies in the past, making weed a performance decreasing drug for him. Fat fool.