Aha! I did find something. I'll look later for info regarding statewide, but here is an article for Philadelhia

graffiti law

"The first step of PAGN was to create tougher anti-graffiti regulations and to increase the intensity of law enforcement. An ordinance made it illegal to sell spray-paints to minors and prohibited unlocked displays of paints in stores. "

Whew, that was time consuming! But in my search I did learn a lot about graffiti!