An obscure regulation designed to close a gun law loophole that allows some people to avoid background checks when purchasing machine guns and silencers has sparked one of the more unusual gun control debates of the year. That’s because those doing the arguing are all gun enthusiasts. Gun control groups have stayed out of this one.

The regulation in question — proposed earlier this year by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) — has drawn more than 9,000 comments. Many are from individuals urged to write the agency by gun groups, according to analysis via Sunlight’s Docket Wrench tool. The comment period for the proposed rule closed on Dec. 9.

They are protesting the agency’s plan to shut down a loophole that allows people to avoid background checks when purchasing sawed off shotguns, machine guns, silencers, guns that look like pens and even Molotov cocktails — all classified as National Firearms Act weapons under a law dating back to 1934, the glory days of Al Capone and Baby Face Nelson — as long as the weaponry is transferred into a legal trust. Usually, purchasers of such weapons must get approval from the ATF, pay a $200 tax, undergo stringent fingerprint-based background checks and get sign off from local law enforcement officials, among other measures.

But if individuals register these firearms to a legal trust or corporation, there is no background check or required approval from local law enforcement officials. In recent years, gun enthusiasts have been flocking to lawyers or creating their own trusts with popular software such as Quicken. The New York Times reported that Christopher J. Dorner, the former Los Angeles police officer who went on a shooting rampage earlier this year, wrote in his manifesto that he’d used Quicken to create a trust where he placed silencers and a short-barreled rifle without having to undergo a background check. (The paper notes, however, that because Dorner was not a felon, he would have passed a background check.)

A Google search for “national firearms trust” returns sponsored ads trumpeting legal services to help people create such trusts. The ATF  reports that applications for transfers of NFA firearms to trusts and corporations has skyrocketed from 840 in 2000 in 2000 to 12,600 in 2009 to more than 40,700 in 2012.

While President Barack Obama claimed the regulation as one of the executive actions he was taking to reduce gun violence following to last year’s shootings at Sandy Hook Elementary School, the ATF had been working on a proposal for many years. In fact, the proposed regulation says it was drafted in response to a 2009 petition by a firearms industry group — the National Firearms Act Trade and Collectors Association (NFATCA). The group had long been seeking that the ATF eliminate the “CLEO” provision, which requires local law enforcement to sign off on NFA weapon transfers. The complaint was that many local law enforcement officials were refusing to do this sign off, thereby preventing such transfers.

But the group felt double-crossed by the ATF once it saw what would be in the proposal. “The proposed [rule] is being used as a political expedient to address areas of negligible concern. The Executive Branch proposals unduly burden the law-abiding public, will restrain lawful commerce and bury an already overwhelmed agency with an administrative infrastructure that will not serve the public safety interest,” wrote the NFATCA’s president, John K. Brown III, in a public statement last August.

Meanwhile, the NFATCA was getting beat up on the Internet by gun enthusiast publications and bloggers for being the inspiration for the new rule. Blogger David Cordrea, who has earned the title of “Gun Rights journalist of the year” from the Citizens Committee for the Right to Keep and Bear Arms for his work on the “Fast and Furious” controversy, has written a series of posts both blasting NFATCA and the ATF proposal. A typical reader comment: “Way to throw your brothers under the bus, traitors.” A spokesman for NFATCA told Sunlight that the group was not responding to requests for interviews but rather directing people to its website for information about its position.

The 9,000-plus comments posted on Regulations.gov and available for viewing here on Docket Wrench appear to come largely from private citizens and are overwhelmingly negative. One cluster of comments appears to be inspired by this alert from Grass Roots North Carolina, which includes such language as, “The resources available to ATF/NFA including but not limiting to NCIC, TECS, NLETS, III, and NICBCS databases more than adequately ensure that all applicants are fully screened.” The acronyms refer to government databases used by Homeland Security that link law enforcement offices together, follow background checks for gun purchases, track crime and so on.

In October, the National Rifle Association encouraged its members to comment. The gun group argues that many people use gun trusts for estate planning reasons, “One of which is to simplify the transfer of the firearms to the heirs of the owner. Thus, children, including those who are very young, are often beneficiaries of trusts. The proposed rule seemingly would require even such children to be included in its expanded background check procedures.”

One of the leading attorneys who has advocated for gun trusts, Florida-based David M. Goldman, whose website is titled “guntrustlawyer.com,” posted his formal comments as well as comment letters from the NRA, NFACTA and others.

Major gun control groups, such as the Brady Campaign to Prevent Gun Violence and Mayors Against Illegal Guns, while supportive, have largely stayed out of the fray. “To get these particularly dangerous guns, the president is doing whatever is within his power to close loopholes in federal law,” said Sam Hoover, a staff attorney with the Law Center to Prevent Gun Violence. However, he said his group had not submitted comments to the ATF. A search of comments does not show any coming from gun control groups, although due to the vagaries of how such searches work it is possible that some may have been missed.