Legal Question in Criminal Law in Michigan

You can contact the local police / sheriff / state police office to investigate the incident. It could go in several directions. A charge like Joyriding could be issued, or a slightly more serious crime of Unlawfully Driving Away an Automobile, or even Larceny By Conversion. It depends on the investigation's information, including how long the vehicle is gone by the time the investigation closes, what (if anything) your grandson says about the matter, etc. Sometimes prosecutors (who charge the case; cops don't charge cases) will not issue if there seems to be more unwritten facts to the case, like a history of this happening over and over and the victim still letting the vehicle be 'borrowed', etc.