Well, yes, but what if convention and tradition forces them to not bring in things they would otherwise like to do? There the rules would be made by the expectation of the people being governed that the conventions and traditions will not be tampered with or scrapped. (It would be a foolish government to just ignore the expectations - yes, they could impose their will by force but there is always the risk there they would be overthrown by force when the people have had enough).
Then there are the rules not governed by law. What religious (if any) rules are there? What are the generally accepted codes of conduct and what happens to those who flout these? Who put these rules together in the first place and has anyone ever challenged them?
So who does make the rules in your stories then? The great thing is lots of stories can come out of how you answer that one.