Dozens of gun-rights advocates testified in Annapolis on Monday on a bill that would ban 3-D printed and other homemade guns that lack serial numbers, what are sometimes referred to as “ghost guns” because they are harder to trace.

House Majority Leader Kathleen Dumais, the bill’s sponsor, told the House Judiciary Committee that the bill is targeted at guns made via 3-D printing or from kits ordered online.

“I became interested in this when a young man went to Clarksburg High School in my district the day after the Parkland shooting with a homemade gun,” Dumais said, referring to the mass shooting at a high school in Parkland, Florida last year.

Though no one was injured by that student at Clarksburg High School, she said, homemade guns have also been used in crimes elsewhere.

“Kevin Neal in California murdered five people with an unserialized rifle that he constructed in Northern California in 2017,” she said. “He was a felon and prohibited from owning firearms.”

California is one of two states that have laws similar to the one Dumais has proposed. In New Jersey, Gov. Phil Murphy signed a ban on ghost guns in November.

In addition to being untraceable, 3-D printed guns are often made entirely of plastic, meaning they can evade metal detectors, said Monisha Smith, the regional director for government affairs at the advocacy group Everytown for Gun Safety.

“Now types of disguised guns which are all built to look like wallets, lighters or cell phones can be easily concealed, which is dangerous for all communities,” she said over the jeers of gun rights advocates.

But dozens of opponents told lawmakers that homemade guns are rarely used in crimes and that 3-D printed guns don’t pose much risk. They’re expensive, they said, and those plastic parts break easily.

John Commerford, deputy managing director of state and local affairs for the National Rifle Association, said building guns at home is a long-standing tradition that pre-dates the United States.

“People manufacture bolt-action rifles for hunting,” Commerford said. “There are kits available online, which you can mill out, create your own gun, at a cost that’s about double the price of purchasing the comparable firearm from a manufacturer.”

“I don’t make my own firearms, but if I want to I believe it’s my right to under the Second Amendment,” said a man who introduced himself as Brian Miller. I should be able to manufacture my own firearm for my use.”

Miller, who told the committee he has been in law enforcement for 18 years and is a school resource officer, said existing laws prevent him from selling or transferring a homemade gun to someone else, or even enlisting someone to help him build it.

Many opponents said that if this legislation passes, they’ll find a way around it, challenge it in court or just flat out disobey the law. Some wore shirts that said, “We will not comply.”

“A lot of people do it because they don’t want to be regulated,” said a man who introduced himself as Chris Rummel. “They don’t want you to know, and quite frankly, it’s none of your business what I have, what I manufacture in my home.”

He told the committee that he’s made a lot of ghost guns, and because the legislation as proposed would make it illegal to own a homemade gun built after 1968, he said it would make him a criminal.

“I’ve made AKs. I’ve made AR-15s,” he said. “It’s not something you do in 10 minutes. You need a proper skillset in order to make it right so that it functions properly.”

Dumais acknowledged that it will be virtually impossible to prevent Maryland residents from ordering the kits or downloading blueprints for 3-D-printed guns. But when someone does, she said, the bill would make it a crime.

The Senate Judicial Proceedings Committee is scheduled to consider that chamber’s version of this bill on Wednesday.