Last month, a video was released of two police officers in Elkhart, Ind., repeatedly punching a handcuffed man in the face. The episode was just the latest in a long-troubled police department where nearly all of its supervisors have disciplinary records.

This is the sort of problem that Congress sought to address in 1994 when it authorized the Justice Department to overhaul troubled local police agencies under court-monitored consent decrees. These agreements lay out a reform plan negotiated by federal law enforcement officials and the local government.

After seeing the videotaped beating, Elkhart’s mayor, Tim Neese, asked the Indiana State Police for a “very thorough and far-reaching” investigation of his police department. But the state police turned him down, so he asked the Justice Department for help. His timing could hardly have been worse. Less than three weeks earlier, Jeff Sessions, who was then the attorney general, had sharply limited the Justice Department’s ability to use court-ordered agreements to address abuses by local police departments. It was one of his last actions before he stepped down.

Mr. Sessions was a longtime opponent of these agreements, complaining that they damaged police morale and smacked of federal overreach. But his critics say his last-minute move is likely to further the Trump administration’s efforts to impede police reforms nationally. For instance, the Obama Justice Department had wanted to revamp the police department in Ville Platte, La., where officers have a long history of jailing people without probable cause. But once Mr. Sessions took over, the Justice Department settled on a watered-down version of the ambitious reform plan Obama administration officials had envisioned. As ProPublica has reported , illegal arrests remain a reality of daily life in Ville Platte.