PHILADELPHIA — Pennsylvania’s two largest cities sued the state Monday over a new law that was designed to let the National Rifle Association challenge local firearms ordinances in court.

The lawsuit is the latest fight between Pennsylvania cities trying to curb gun violence and a legislature that has resisted new forms of gun control in a state rich with hunting tradition.

The lawsuit, filed by Philadelphia and Pittsburgh, argues lawmakers approved the measure in violation of state constitutional provisions designed to promote transparency in the legislative process.

“We’ll fight this effort in every possible step. We’re doing the right thing in trying to make people safe,” said Philadelphia Mayor Michael Nutter. “The NRA is wrong again, as usual.”

Other plaintiffs include the city of Lancaster and five Democratic lawmakers from Pittsburgh and the Philadelphia area.

State Sen. Daylin Leach, D-Montgomery, said “the way this bill was passed was such an egregious violation of the basic rules of legislating that we felt compelled to act.” He said the law allows the NRA “to sue our own citizens for protecting themselves and their communities.”

In general, Pennsylvania bars its municipalities from enforcing firearms ordinances that are stronger than state law. But the NRA has complained dozens of local ordinances go unchallenged in Pennsylvania courts by residents who can prove it harmed them.

Under the new law, a gun owner would no longer have to prove they had been harmed by the law to successfully challenge it, and “membership organizations” could stand in to sue on behalf of any Pennsylvania member. The challenger also could seek damages, and the law’s opponents fear a wave of expensive lawsuits against municipalities.