According to the california code:
http://www.leginfo.ca.gov/cgi-...26712
d) Notwithstanding subdivision (a), clear, colorless, andtransparent material may be installed, affixed, or applied to thefront side windows, located to the immediate left and right of thefront seat if the following conditions are met: (1) The material has a minimum visible light transmittance of 88percent.
Basically, you can have a tint of 88% or higher, which is barely noticeable. Another reason why I or you shouldn't live in California, dumb laws they implement.