I think you are misinformed.
I would love to be corrected on this.
I believe they have a preemption law, but it has no teeth, no way to force compliance.
A statute with teeth was passed a couple of years ago, and signed into law; but a corrupt AG (she went to prison) and cities took it to court and had the law thrown out on an almost never used technicality.
The end result was the cities (particularly Philadelphia) simply ignore the law, and pass illegal ordinances.
They pass them.BUT,If they try to enforce them on you you will win in court The last one with TEETH was thrown out because an outside organization such as the NRA was able to join you in the case .That became a no no.The only entity that can pass legal firearms laws is the State legislature.