Colosimo's has been charged with making false statements and failing to properly maintain firearms transaction records.
The U.S. Attorney's Office announced charges against Colosimo's Inc. after business hours Tuesday. A man who answered the phone at the business said "What can I say?" to a reporter seeking comment and eventually hung up. Owner James Colosimo has previously said he follows all laws in his business.
Though Colosimo's is part of a federal investigation, there's been a local crackdown on straw purchases in recent years with the Philadelphia gun violence task force seizing 673 firearms involved in straw purchases since December, 2006.
The protesters believe the charges against Colosimo's shows progress.
"A big step has been made, but many more steps need to be made," said Fr. Joseph Genito of St. Rita's of Cascia.
Other protesters say lying about buying needs to stop.
"It was my son 20 years ago," said Cherie Ryan of Mothers in Charge. "If these straw purchases continue, it will be someone else's son tomorrow."
Activists have targeted Colosimo's because of the number of guns sold there that end up being used in crimes. The owner has said that's to be expected from a high-volume dealership like his. He has said he believes he has saved lives by selling guns to police departments.
The Associated Press contributed to this report