I did not find any new STATE law for PA regarding the refrigerant. However, State law can not be less restrictive than federal law on environmental issues. (But, nothing prevents it from being MORE restrictive than federal law). The federal EPA rules on R12 refrigerant are such that production of NEW r12 stopped in 1995 for most purposes.
All R12 legally available today is either recycled (not completely pure), or reclaimed (Pure as new r12), or someones stockpile of original unsold r12. Federal EPA prohibits the mixing of alternative refrigerants (such as r134a) with R12 or with each other. Lengthy and detailed requirements are promulgated by EPA regarding recycling equipment, labels, thread sizes/pitch/direction, connecter types, etc. to preclude this possibility. The Automotive AC specialist must take great pains to make sure that all the R12 is removed for recycling and that the system is converted to a product specific system before the alternative refrigerant can be added.
In this sense, your dealer can not add r134a to your r12 system without legally converting it first, if that is what you were asking. If you want him to add more r12 to your r12 system, he or she can do that if it is not leaking, presuming they can get any r12. If it is leaking, they must repair or convert it first. PA may also have a new local law that I didn't find precluding sale of r12, or prohibiting addition of refrigerant to a leaking system (also against Federal EPA regs!).
Hope this helps.
[Edited by JCE on 05-07-2001 at 11:35 PM]