The US Court of Appeals for the Sixth Circuit affirmed a government ban on firearm accessories known as bump stocks, a device that modifies semi-automatic rifles to fire more rapidly, in Gun Owners of Am., Inc. v. Garland Friday.

The Trump Administration outlawed bump stocks after a 2017 shooting in Las Vegas where the rapid-fire accessory was used to kill 58 people. In March, the Court of Appeals for the Sixth Circuit rejected a Bureau of Alcohol, Tobacco & Firearms (“ATF”) interpretation that bump stocks constituted an illegal “machine gun” under federal law.

This ruling overturned a district court ruling to the contrary. The Appeals Courts majority concluded that the ATF’s interpretation was not eligible for Chevron deference. However, in June the court granted a petition for rehearing en banc (with a full bench). 

Friday’s decision affirmed the original district court’s judgment. The court split 8-8 allowing the lower court decision to stand. A majority vote was needed to overturn the lower court. The judges disagreed over whether a bump stock qualifies as a “machine gun” under 26 U.S.C. § 5845(b) and, insofar as the statutory language is ambiguous, whether the ATF’s interpretation merits Chevron deference given that unlawful machine gun possession is a criminal offense.

A separate challenge to the bump stock rule also occurred when a Tenth Circuit panel affirmed a lower court’s refusal to lift the ban. The full Tenth Circuit agreed to hear the case but later decided to drop it. The bump stock proponents in that case are seeking US Supreme Court review.