Why do civilizations have laws?

I think civilization have laws because then the ruler of the land could still have power to controll his people. When people break laws they get punish and that i think is what makes the ruler more powerful. If you get punish you probably wouldn't like it and so you follow the laws made, then you won't get into trouble, and that kind of means you are listening to the ruler (obeying him/her)That is why I think civilization have laws.