The city filed a civil suit against Rashad Armstrong, a Philadelphia man who, the suit contends, knew in April 2018 that his gun had been lost or stolen but didn't report it.
The gun was found, along with drugs, on a Lancaster man during a traffic stop by Lancaster police a month later. The suit says Philadelphia police questioned Armstrong about the gun — a Ruger semi-automatic — in June of that year and he told them it had been taken without his permission.
Efforts to reach Armstrong were unsuccessful.
He is the first person the city has pursued under the 2008 law, one of five passed that year aimed at curbing gun violence. Then-District Attorney Lyn Abraham said she would not enforce the laws because she believed they violated state law.
But DA Larry Krasner announced in January that he was working with the city's Law Department to begin enforcing the reporting requirement.
City Solicitor Marcel Pratt said he can't speak to Abraham's opinion but as the city's chief legal officer, he believes it does not conflict with state law.
"I think the city is on extremely strong legal ground that our ordinance is not pre-empted. This ordinance is 100 percent legal and we're moving forward with enforcement," Pratt said.
Mayor Jim Kenney said it's a long overdue step.
"You need to take responsibility for being so reckless with your weapon that it's stolen from your car or stolen from your house," Kenney said.
The law's author, Council President Darrell Clarke, said he expects a challenge from gun rights groups but that the measure is simple common sense.
"Somebody steals your vehicle, you call the police; you lose your credit card, you call your bank; you lose your gun, you don't call anybody? This is a no-brainer," Clarke said.
Clarke said it's a common practice for "straw purchasers" to sell or give a gun to someone who is not allowed to own one because of a previous criminal conviction, then — if the gun is used in a crime — to claim it was lost or stolen.
"We have to get the weapons off the street and I think this is probably the most significant move to doing that since I've been a council member," he said.
The suit against Armstrong seeks a $2,000 fine.