The laws governing the legal use, storage and carrying of firearms are constantly changing. Below are the applicable laws in the State of Michigan as of 2/21/2013. The below information is designed to be a guide and not the final word. If you have specific questions, please refer to the State of Michigan legislation at legislature.mi.gov. Another great resource is the the Michigan State Police Department and can be found at michigan.gov/msp.

MCL 750.231a   A person is now permitted to transport a pistol for a lawful purpose if the owner or occupant of the vehicle is the registered owner of the firearm and the pistol is unloaded and in a closed case in the trunk of the vehicle. If the vehicle does not have a trunk, the pistol may be in the passenger compartment of the vehicle unloaded and inaccessible to the occupants of the vehicle. 

A 'lawful purpose' includes:

While en route to or from a hunting or target shooting area.
While transporting a pistol to or from home or place of business and a place of repair.
While moving goods from one place of residence or business to another place of residence or business.
While transporting a licensed pistol to or from a law enforcement agency for the purpose of having a safety inspection performed (registering the pistol) or to have a law enforcement official take possession of the pistol.
While en route to or from home or place of business to a gun show or place of purchase or sale.
While en route to or from home to a public shooting facility or land where the discharge of firearms is permitted.
While en route to or from home to private property where the pistol is to be used as permitted by law, rule, regulation, or local ordinance.