The answer to this is almost always, no! While the law may differ in some states slightly, in most places it is illegal to place a GPS tracker on a vehicle that one does not personally own. You can have a GPS placed on your own car or on a car that you are letting your child drive or somebody borrow, but you have to own the vehicle. If a private investigator tells you he or she can place a tracker on somebody’s car, you should question it. It is likely against the law.