If as you say, those laws were around for a long time among humanity before they were handed to Moses on the Mountain, it doesn't prove they were not written by God and handed out to others at an earlier time.
Hammurabi was a prophet! :(
These laws were written by people who had never even heard of your god. They had their own gods. These basic rules were merely found over the years to be the best way for man to act in order to promote a stable society, given the nature of man and dynamics of society. Giving man-made laws the force of god in order to make them more likely to be followed has been around as long as religion.