AUGUSTA — Lawmakers gave initial approval Thursday to a bill prohibiting undetectable firearms and requiring serial numbers on firearms.

The House advanced the bill on a 77-70 party-line vote, with Democrats in support and Republicans opposed, while the Senate advanced the bill on a narrow 18-17 vote with Sen. Joe Baldacci, D-Bangor, and Sen. Craig Hickman, D-Winthrop, joining Republicans in opposition.

Similar bills have failed in previous Legislatures, but the latest push comes in the aftermath of the high-profile killing of a health care CEO in downtown Manhattan last year involving a so-called ghost gun. Ghost guns are untraceable firearms, often assembled at home or by mail-order kit, that are not marked with serial numbers.

The bill faces another round of votes in each chamber, and will also need to compete with other bills for funding before it could be sent to Gov. Janet Mills for her consideration.

It was among more than a dozen pieces of legislation related to firearms taken up in the House and Senate Thursday, including a ban on bump stocks and other rapid fire devices that was defeated in an initial Senate vote.

Rep. Sam Zager, D-Portland, the sponsor of the bill on ghost guns, said during Thursday’s floor debate that requiring serial numbers and prohibiting untraceable firearms is critical for enhancing public safety and giving law enforcement the ability to trace weapons used in crimes.

“Passing LD 1126 will ensure our law enforcement agencies are fully equipped to investigate and trace guns found at crime scenes while upholding the constitutional rights of all Mainers,” Zager said.

Unserialized firearms are increasingly used by domestic terrorists and arms traffickers because they can’t be traced, he said, while serial numbers are critical in helping law enforcement with investigations. “Each time a law enforcement officer in this state, and this country, performs a trace, they are essentially attesting to the notion that serialization aids in their investigation,” Zager said.

Federal law requires that firearms manufactured for sale in the United States have serial numbers stamped on them and it’s a crime to obliterate or obscure a manufacturer’s serial number. The U.S. Supreme Court also ruled in March to uphold Biden administration rules that guns built from at-home kits be treated like other firearms by requiring companies to add serial numbers, run background checks and verify that buyers are 21 or older.

Still, the rise of the at-home kits and 3D printing to assemble firearms have made it easier for the rules to be skirted and for untraceable firearms to be circulated.

Fifteen states have banned ghost guns, including Massachusetts and Rhode Island, according to gun safety organization Everytown for Gun Safety.

“Recent advances in technology and materials have created a dangerous loophole,” Zager said. “In Maine, law enforcement agencies are contending with an increasing prevalence of unserialized firearms … assembled by individuals at home, not firearms manufacturers.”

The use of ghost guns in crimes has increased by more than 1,000% since 2017, according to a U.S. Department of Justice study released in 2023. One high-profile recent example was when 26-year-old Luigi Mangione allegedly used a ghost gun to kill UnitedHealthcare CEO Brian Thompson.

The bill would make it a Class C crime to manufacture or sell an untraceable firearm and a Class D crime to intentionally or knowingly possess an untraceable firearm. Firearms that meet a federal definition of curio or relic would be excluded.

Rep. Jim White, R-Guilford, a firearms dealer and gun shop owner, was among Republican lawmakers who spoke against the proposal Thursday. White said that tracing firearms can be a complicated and lengthy process and a serial number is not a guarantee a crime will be solved or the owner of the weapon will be tracked down.

“There is no protection given by serializing a firearm,” White said. “All it is is a method to assist law enforcement in tracing the history of that firearm. And there’s no guarantee of an outcome that’s not a dead end.”

Sen. David Haggan, R-Hampden, argued that the ability to build firearms at home is a “constitutionally protected activity” and that restrictions would likely be found unconstitutional. He also raised questions about the ability of firearms dealers to serialize guns for people who build them at home.

“There is a lack of firearms dealers that can perform such serializations,” Haggan said. “There aren’t a lot of people who can do these things… They also don’t want to open themselves to liability for issues with a firearm they did not manufacture.”

SENATE REJECTS BUMP STOCK BAN

The Senate voted 19-16 Thursday against LD 677, a ban on bump stocks and other rapid fire devices that increase the rate of fire of semi-automatic weapons so they function more like machine guns. A similar measure was passed by lawmakers but vetoed by Gov. Janet Mills last year.

Mills cited the fact that federal regulations banning bump stocks were being challenged at the time in the U.S. Supreme Court — which did eventually strike down a federal ban on the devices — and also voiced concerns about the language of last year’s bill being too broad and ambiguous.

Carney said in March that the high court’s ruling that the Bureau of Alcohol, Tobacco, Firearms and Explosives had exceeded its statutory authority with the regulations added urgency to the need to approve a state-level law. She said the bill also includes different language than last year’s to address concerns from Mills that it would inadvertently prohibit adjustments made by hunters to improve accuracy rather than change the rate of fire.

The House on Thursday rejected a bill to prohibit the possession of large-capacity ammunition feeding devices and a bill that would allow municipalities to prohibit firearms in municipal buildings and voting places.

They gave initial approval to a bill to facilitate firearms hold agreements through which people could temporarily store their firearms with a gun shop. That bill was sponsored by Rep. Stephen Wood, R-Greene, but also gained the support of some Democrats Thursday.

It was introduced with the intent of helping veterans and first responders going through a mental health crisis, though a similar Democrat-sponsored bill sought to facilitate the agreements for other groups, such as people selling their homes or those who have visiting family and thus wouldn’t want firearms around.

“I support this bill,” said Rep. Adam Lee, D-Auburn. “I think it’s a good bipartisan solution for folks who are in crisis and want to temporarily relinquish their firearms, but don’t want to do so by court order. I think we should give every opportunity for those folks in crisis to avoid the potential devastating outcomes of remaining with those firearms.”