In the lawsuit in filed Thursday in U.S. District Court in Maryland, the plaintiffs argues the the Second Amendment and case law protect their right to own assault rifles and magazines that hold more than 10 rounds, The Baltimore Sun reported.
The new gun law Maryland lawmakers passed earlier this year bans 45 types of assault weapons, but people who own them now will be able to keep them. The law also limits handgun magazines to 10 rounds and requires people to submit fingerprints to the state police to get a license to buy a handgun.
A spokeswoman for the National Rifle Association told The Baltimore Sun lawyers for the plaintiffs plan to ask a judge Friday for an injunction to prevent the law from taking effect.
A spokeswoman for Gov. Martin O’Malley, a Democrat, said she expects the law will withstand the group's legal challenge.
"The vast majority of Marylanders support these common-sense efforts to reduce gun violence," spokeswoman Samantha Kappalman told the newspaper. "The new law will take effect on Tuesday, and it will make families safer."
John Josselyn, Associated Gun Clubs of Baltimore's legislative vice president, said in a statement that the restrictions are "an unconstitutional violation" of the Second Amendment rights of "law-abiding, responsible citizens."
"Together we are drawing a line in the sand where Maryland’s gun control agenda tramples the fundamental individual right to defend oneself and family in the home," Josselyn said.
A spokesman for the Associated Gun Clubs of Baltimore Inc., one of the plaintiffs, said the new laws would keep honest citizens from being able to "choose effective firearms for defense in the home."
The pending new law has prompted a huge increase in applications for firearm purchases, and a backlog has resulted. In the last two weeks, state troopers said applications are coming in at the rate of 1,000 per day.
Maryland State Police said Tuesday residents who have submitted handgun purchase applications before new requirements go into effect next week will not have to obtain a handgun qualification license.
The agency said that troopers will not enforce the new requirements, which also include background checks and fingerprinting, on applications submitted by Sept. 30.
Troopers said as of Friday, slightly more than half of the more than 100,000 purchase applications received had been processed.
The agency began 24/7 operations in December to process the applications, but the backlog continued to grow.
Earlier this month, state police said 20 law enforcement officers from other agencies began helping with background investigations. State law requires that the investigations be conducted by police officers.
Troopers also said that beginning last week, 24 data entry employees from the Maryland Department of Public Safety and Correctional Services have been inputting information from applications. State police said several security measures were being taken to limit the access of DPSCS employees to the State Police database.