If someone has a car registered, licensed and insured in a given U.S. state, and intends to travel across state and province lines, are they supposed to make sure that they're in compliance with the window tinting rules and laws in all such states and provinces, or is it sufficient that the car is in compliance with the laws in the U.S. state where it's coming from?
Whether your car is street legal in State A is determined entirely by the laws of State A.
If the law of State A states that only a certain level of tint is acceptable, and doesn't make an exception for out-of-state registrations, you will be in violation. You may or may not get a ticket if you're just passing through, but if you do get one, you won't have a defense to it.
The only way the law of State B would matter would be if:
- The law of State A actually incorporated State B law by saying something like, "...unless the vehicle is registered in another state, the driver is a resident of that state, and the vehicle is in compliance with that state's laws.
- The law of State A was independently unenforceable, either as written or as enforced; for example, if it affected some federal Constitutional right (e.g., "Cars driven by suspicious-looking people may not have tinted windows," with only Black drivers being ticketed).