It’s a bit vague on the actual law.
For example, I can tint any window behind the driver as dark as I want on my SUV. Right from the factory it has really dark tint on the back windows.
According to the NY State Vehicle and Traffic Law under section 375-12, if you have a 1992 or later model year passenger car or station wagon, the side windows adjacent to AND behind the operators seat must have a light transmittance of SEVENTY PERCENT or greater. If you own a vehicle classified by the EPA as a truck or light truck ONLY the area BEHIND the operators seat may be tinted with a tint less than seventy percent. These types of vehicles include but are not limited to: SUVs, Mini Vans, Full size vans and Pick up trucks. All types of vehicles 1992 or later, the windows adjacent to the operators seat must have a light transmittance of seventy percent or greater. If your vehicle is older than a 1992 it must conform to a older V&T section which was a light transmittance of greater than thirty five percent. This section was first written in the 1985 era.