Answer:
Window tinting laws vary from state to state, however there are some general guidelines, for example windshields must not be coated in reflective tinting, and the tinting must be above a certain line on the windshield, though that line varies depending on the state. Other laws are very different, for example in California, Back Side and Rear windows can be any level of darkness, but in Alabama, Front, Back and Rear windows must all let more than 32% of visible light into the car.