This is the actual LAW passed by the PA Legislators in response to the will of the people. If an officer cites you, this is the law that he will probably accuse you of violating!
TITLE 75 Section 4524 (e)(1) of the Pennsylvania Common Statutes states that
(1) No person shall drive any motor vehicle with any sun screening device or other material which does not permit a person to see or view the inside of the vehicle through the windshield, side wing or side window of the vehicle.
Note that the law only prohibits tinting which prevents a person from seeing or viewing the inside of the vehicle. It does not prohibit all tinting or tinting below 70%. The Law therefore implicitly permits any tinting which does not prevent a person from seeing or viewing the inside of the vehicle.
Note also that it does NOT say that a person must be able to view the inside of the vehicle, only that the tint cannot prevent a person from seeing in. (no one can see into a vehicle at night, even with clear windows) Also the way the law is stated it is only requiring that a person be able to see the inside either through the windshield, side wing OR side window. If the word 'and' was used instead of 'or' it would require viewing through all of the mentioned windows.