PoA is centralized, by definition. You are approved to be a validator by some trusted entity. In theory, this can be a group or consensus (you could imagine a

PoA is centralized, by definition. You are approved to be a validator by some trusted entity. In theory, this can be a group or consensus (you could imagine a PoA scheme where the set of authorized validators is passed around like a HOSTS file), but you still need to trust the mechanism that authorizes validators. You lose your right to be a validator through misbehavior; you are removed from the list of authorized validators, and hence can't do it anymore.