Vermont Gov. Phil Scott, a Republican, has allowed a bill to become law that requires serial numbers on firearms that are privately made with individual parts, kits or 3D printers.

Scott allowed the bill, part of an effort to crack down on hard-to-trace ghost guns that are increasingly showing up in crimes, to become law without his signature. He said in a letter to lawmakers Tuesday that while he agrees that firearms should be serialized as a public safety measure, he has concerns about the law’s “practicality and impact.”

“Over the last decade, as anti-policing policies increased and criminal accountability has steadily decreased, violent crime has grown in Vermont,” Scott wrote. “This is why I believe we should instead focus on measures that will reverse these trends over those, like S.209, that are unlikely to have any measurable impact on violent crime.”

Supporters of the measure in the Democratic-controlled Legislature have said it’s critical for Vermont to keep the weapons out of the hands of people who aren’t allowed to have firearms. The U.S. Supreme Court agreed last month to take up a Biden administration appeal over the regulation of the difficult-to-trace ghost guns.

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The law in Vermont, a politically liberal state that also has a strong gun and hunting culture, includes penalties ranging from fines to prison time depending on the offense. A person who carries a firearm that lacks a serial number while committing a violent crime would face up to five years in prison, a maximum fine of $5,000, or both.

Chris Bradley, president of the Vermont Federation of Sportsmen’s Clubs, said last month that the legislation is a tax on law-abiding gun owners who would have to get a gun serialized and undergo a background check.

The measure also prohibits guns at polling places. The secretary of state’s office, in consultation with the Vermont League of Cities and Towns and the Vermont Municipal Clerks and Treasurers Association, also is required to report to the Legislature by Jan. 15 on options for prohibiting firearms in municipal and state buildings, including the Statehouse, which some Republicans fear would lead to further gun restrictions.

Vermont is the 14th state to regulate ghost guns, according to Vermont chapters of Moms Demand Action and Students Demand Action.