This is from my 2000 Vehicle Code book (I know it's old, but I'm pretty sure it still applies):
Material Obstructing or Reducing Drivers' View (26708.2)
No person shall drive any motor vehicle with any object or material placed, displayed, installed, affixed, or applied in or upon the vehicle which obstructs or reduces the driver's clear view throught the windshield or side windows.
Clear, colorless, and transparent material may be installed, affixed, or applied to the front side windows, located to the immediate left and right of the front seat if the following conditions are met:
1. The material has a minimum visibile light transmittance of 88%.
2. The window glazing with the material applied meets all requirements of Federal Motor Vehicle Safety Standards No.20 (49 C.F.R. 571.205), including the specified minimum light transmittance of 70% nad the abrasion resistance of AS-14 glazing, as specified in that federal standard.
3. ...enhance the ability of the existing window glass to block the sun's harmful UVA rays.
4. ...has a certificate signed by the installing company ... and the manufactuer
In short, the way that I read it, they say that a sunscreening device on the front side windows, unless "clear, colorless, and transparent", must be accompanied by a letter from a physician certifying that they must be shielded from the sun due to a medical condition. Most of the time, if they can see you through the window, they won't bug you. Just don't drive around like a jacka$$ and they usually won't even notice. And no reflective tint either.
-mike
