@beoran A “Free City” was ‘free” by permission. Period. They were granted limite

@beoran A “Free City” was ‘free” by permission. Period. They were granted limited autonomy, as a means of increasing revenues to the ruling aristocracy, and limiting the costs of administration by the state. https://en.wikipedia.org/wiki/Free_imperial_city

They weren’t a check. They were just sufficiently organized with capital in sufficient concentration that the empire didn’t need to govern ( render justice) in them in order to produce order and ’empty the woods of brigands”. This is partly because those free cities were founded by the nobility and had their own arms and justice.