call your local game department, they will tell you about the crossbow. It varies from state to state. a 2 min phone call could keep you from alot of trouble.
PA generally allows felons to possess bb guns, but CO2 guns could be another matter.
Some cities in PA (PHL for example) prohibit felons to possess any bb gun, CO2 gun, or REAL gun.
You should check with your local police or sheriff's office for your own protection and safety.