california law is 70% total transmission for the front, and no limit to the back as long as you have two side mirrors, on old cars with only the drivers side mirror, they are not allowed to tint the bakc window at all.. The factory tint is about 80% on honda so pretty much any tint at all on the front windows is illegal. I had 35% front and 5% rear, but got a ticket, so I went to 55% front and 5% rear which still protects the inside of the car, keeps it nice and cool in the summer, and even after getting pulled over a few times for other violations(1 speeding, 2 noise pollution, 1 no front plate, and 1 just to screw with me) They've never said anything about my tint.

 

I have 35 all around including the front. Haven't got stopped for it yet either. I even had to take my car up to the police station for them to verify i changed some crappy temp blue euro lights in the corners and the cop still did not notice the tint...i'm in alabama tho