those limits were what was the window tint law enacted in 1999 unless they changed back after 1999 the back and rear windows can be as dark as you like.I might look that up before I went super low on the back windows in California. I know from experience that 5% in the back is illegal and will get you a ticket. UNLESS the law has changed in the last handful of years anyways.
CALIFORNIA WINDOW TINT LAW ALLOWS THE FOLLOWING DARKNESS FOR CAR WINDOW TINTING
The darkness of tint is measured by (VLT%) Visible Light Transmission percentage. In California window tint law, this percentage refers to percentage of visible light allowed to pass through the combination of film and the factory tint of the window.
Here is what is allowed in California window tint law:
WindshieldNon-reflective tint is allowed on the top 4 inches of the windshield.Front Side Windows Must allow more than a total of 70% light in. Transmission through glass.Back Side Windows Any VLT can be applied legally on this window.Rear Window Any VLT can be applied legally on this window.