HARRISBURG — A Pennsylvania state court on Thursday struck down a law designed to make it easier for gun owners and organizations like the National Rifle Association to challenge local firearms ordinances in court.

The Commonwealth Court said the procedure the Republican-controlled Legislature used to enact the law in the final days of last year’s session violated the state constitution. The ruling came after dozens of municipalities had already repealed their gun laws.

Under the law, gun owners no longer had to show they were harmed by a local ordinance to challenge it, and it let “membership organizations” like the NRA sue on behalf of any Pennsylvania member. The law also allowed successful challengers to seek damages.

The NRA’s lobbying arm had called the measure “the strongest firearms pre-emption statute in the country.”

Five Democratic legislators and the cities of Philadelphia, Pittsburgh and Lancaster sued to block the law, saying it was passed improperly. The GOP defendants included House Speaker Mike Turzai and then-Gov. Tom Corbett, who lost his bid for re-election last year.

Thursday’s ruling sends “a very strong message to the General Assembly that the old way of doing business just isn’t acceptable anymore,” said Mark McDonald, press secretary to Philadelphia Mayor Michael Nutter. “The law requires and the public expects transparency, deliberation and public debate.”

Said Pittsburgh Mayor Bill Peduto: “I’m overjoyed that the court system is joining us in standing up for citizens and public safety instead of special rights for the gun lobby.”

CeaseFirePA, a statewide group that works to stop gun violence, declared the ruling “a huge victory against the NRA.”

Pennsylvania, which has a strong tradition of hunting and gun ownership, has long prohibited its municipalities from enforcing firearms ordinances that regulate the ownership, possession, transfer or transportation of guns or ammunition. Gun-rights groups complained that scores of municipalities ignored the 40-year-old prohibition by approving their own gun restrictions.

The NRA seized on the new state law to challenge gun measures in Philadelphia, Pittsburgh and Lancaster.