When was the first city-states form in mesopotamia?

The first law ever to be written was first believed to be the Code of Hammurabi but there was later discovered an earlier text which revealed a code written by a Sumerian King named Ur-Nammu who predates Hammurabi by three centuries. While the code of Hammurabi is flawed by it's notion of divine right to rule, it does bring to law important understandings about false accusations, property rights, theft and entering into contracts.