“All authority in heaven and on earth has been given to me.” Jesus. (Matt 28: 18a)
So, God, Himself, is the source of ALL authority. Authority can only be conferred. No person can, therefore, steal authority. Power, however, is stealable and prone to it. Might, without authority, can never make right.
Evil men may seize power, but seized power without authority will ever remain illegitimate.