How do you report someone with no auto insurance?

I know someone that has had no auto insurance for over a year. How do you turn them in. Who do you call? first of all I just asked a simple questin. I did not put all the information because I did not think it was important to know why I needed to know. The full details are not important to any one but me. It was and is just a SIMPLE questin. If you don't have an answer without being rude please don't answer!