Tints laws by state, 70% is stock tint.
BTW, primary legal intention for no
front side window tint is traffic safety. Making eye contact with other driver's is more difficult behind tint. Tint laws have nothing to do with the safety of officers, although that is an unintended side benefit. If officer safety was the intention of tint laws, windowless cargo vans would be illegal.
http://www.tintdude.com/laws.html