The retreat by the Justice Department effectively allowed a pillar of the Prohibition-era National Firearms Act to lapse.

© Erin Schaff for The New York Times

Several factors converged to force a remarkable shift in the federal government’s aggressive efforts in Minnesota.

© Victor J. Blue for The New York Times

The National Rifle Association and others have argued citizens need guns to fend off government. The killing of Alex Jeffrey Pretti, who carried a pistol, set off debate.

© Nathan Howard/Reuters