The Bureau of Alcohol, Tobacco, Firearms and Explosives published a final rule in the Federal Register on May 6 formally removing the language that had classified bump-stock-type devices as machine guns, completing the regulatory correction required by the Supreme Court's June 2024 decision in Garland v. Cargill. The rule, document 2026-08926, took effect on the date of publication.

The 2018 Obama-era rule had amended three sections of Title 27 of the Code of Federal Regulations — Parts 447, 478, and 479 — by inserting two sentences into each regulatory definition of "machine gun." The first sentence defined "automatically" and "single function of the trigger" to encompass bump-stock operation; the second expressly named bump-stock-type devices as machine guns subject to NFA registration requirements. The Court's Cargill decision held unanimously that a semi-automatic rifle equipped with a non-mechanical bump stock does not fire more than one shot by a single function of the trigger and therefore does not qualify as a machine gun under the statute. The new final rule strips both sentences from all three regulatory sections. The core machine gun definition — covering any firearm that shoots automatically more than one shot without manual reloading by a single function of the trigger — remains unchanged, as do the provisions covering conversion parts and auto-conversion kits.

The rule was published as a standalone final rule, separate from the package of 21 proposed rule rollbacks the DOJ published on May 5. AmmoLand reports that some 2A commentators consider the change incomplete, arguing that ATF should take the opportunity to clarify other edge cases in the machine gun definition that post-Cargill lower-court litigation has exposed. ATF did not open a comment period for the final rule, citing the Cargill decision as a direct mandate. Several pending criminal appeals by defendants convicted under the 2018 rule before Cargill are expected to benefit from the regulatory cleanup, though individual outcomes depend on appellate procedural posture. State laws in California, New York, and several other jurisdictions independently ban bump stocks and are unaffected by the change to federal regulations.

With the regulatory text now aligned to the Court's ruling, FFLs and NFA dealers have clear guidance that bump-stock-type devices no longer require registration as machine guns at the federal level. Legal observers will be watching for any follow-on guidance from ATF clarifying the treatment of pending or previously denied NFA applications that were based on the now-vacated definitional language.