of the classical world. The Roman state was an authoritarian regime; in other words, dissent was rarely tolerated and government usually responded to protest with violence (especially in the cities of the East where people were often fearless in making fun of emperors). Yet a strong tradition of Roman law had emerged by the fourth century, and this acted as a brake on even the most fearsome emperors. Emperors were not free to do whatever they liked, and the law was actively used to protect civil rights.
That is why in the later fourth century it was possible for powerful bishops like Ambrose to confront equally powerful emperors when they were excessively harsh or repressive in their handling of the civilian population.