WASHINGTON — Former Attorney General Jeff Sessions has drastically limited the ability of federal law enforcement officials to use court-enforced agreements to overhaul local police departments accused of abuses and civil rights violations, the Justice Department announced on Thursday.

In a major last-minute act, Mr. Sessions signed a memorandum on Wednesday before President Trump fired him sharply curtailing the use of so-called consent decrees, court-approved deals between the Justice Department and local governments that create a road map of changes for law enforcement and other institutions.

The move means that the decrees, used aggressively by Obama-era Justice Department officials to fight police abuses, will be more difficult to enact. Mr. Sessions had signaled he would pull back on their use soon after he took office when he ordered a review of the existing agreements, including with police departments in Baltimore, Chicago and Ferguson, Mo., enacted amid a national outcry over the deaths of black men at the hands of officers.

Mr. Sessions imposed three stringent requirements for the agreements. Top political appointees must sign off on the deals, rather than the career lawyers who have done so in the past; department lawyers must lay out evidence of additional violations beyond unconstitutional behavior; and the deals must have a sunset date, rather than being in place until police or other law enforcement agencies have shown improvement.