Usually, the tint you see on new cars in the dealer show rooms is the max allowable tint, which is why, in California, you are not allowed to add any tint to the front driver and passenger windows. There are some states that allow dark tint, however, the CHP addressed that issue stating that if an out-of-state car has an illegal California tint, that vehicle is citable.
The exception is a doctor's note for a medical condition.
I once stopped a very attractive girl for tinted windows, it was high noon during the summer. She showed me a doctor's note for a skin condition. I told her she must know a doctor to have gonna that note since she was wearing a haltered top and shorts in the bright sun. I say she must know a cop too, to know that loophole in the law. I showed her the exception in the vehicle code book and asked her if she meant that exception. She said yes. I asked her to read the last line, "devices described in this section may not be used during hours of darkness." She asked, "What does that mean?". I told her windows shades. She said, "But it would ruin the looks of my car!". I told her, that meant she was doing it for looks and not a medical reason, sign here, press hard please.
Oh, by the way, I've cited people for the same offense twice, but I also cite for failure to comply. That's a $150 fine plus 1 point on your record.
