The federal rule change was hotly contested by the gun industry, which argued that the move could lead to an eventual federal firearm owner registry. In August, a federal judge in North Dakota rejected a lawsuit levied by gun-rights groups and 17 states to block the new regulations.

“This is sort of the standard pattern,” said John Donohue, a professor of law and economics at Stanford University. “The industry fights regulation, then guts regulation, and at the very least, leaves themselves an easy workaround.”