There have been many different stories from customers that tint laws may even be enforced differently by each regional Police Department in the SAME state. In all cases, refer to you local authority for enforcement policies, window tint laws, rules and/or regulations as the final authority to car window tint laws in your area.
Most times these situations are not due to negligence by the police, but lack of clarity in terms of how the state window tint laws were written.
Let's use the Texas Tint Laws as an example. In the state of Texas Tint limit is around 25% or above. This means the darkest tint to have safely would be 25% light emission. 20% is the legal limit but sometimes it is argued that 30% is the legal limit. This limit is for each vehicle on the road.
According to Section 547.613 of Texas transportation the Texas Transportation Code makes it a misdemeanor to operate a vehicle with an object or material attached to the windshield, rear, or side windows that obstructs or reduces the driver’s visibility.
Other rules and regulations are that The tint color(s) of red, blue, and amber are not legal by state law. If back window is tinted then the dual side mirrors are required. The sticker to identify legal tinting is required between the film and glass on the driver's side window. Also, manafacturers of film need to cerify the film they sell in the state.