這是我看到的：California Window Tinting Laws

Window tint darkness

The amount of light that can pass through your car windows is measured in percentages (called VLT), so make sure your tinting film is up to these standards! In California there is no difference in regulations for sedans, or SUVs and vans, so these laws are for all vehicles.

• Windshield doesn’t legally allow any tinting applied to it
• Front side windows must pass through more than 70% of light inside your car (70% VLT)
• Back side windows and rear window can have any darkness

http://www.californiacarlaws.com/window-tint/