WASHINGTON — The Justice Department moved on Tuesday to allow federal inmates to remain on home confinement after the government declares an end to the Covid emergency, reversing a Trump-era legal opinion that said the Bureau of Prisons would have to recall them to federal facilities.

The shift was a rare instance in which Attorney General Merrick B. Garland reversed a high-profile decision made under the previous administration, and a victory for criminal justice advocates who had been pressuring the Justice Department on the issue.

“Thousands of people on home confinement have reconnected with their families, have found gainful employment and have followed the rules,” Mr. Garland said in a statement.

Congress gave the Bureau of Prisons the authority to release thousands of federal inmates to home confinement as part of the Coronavirus Aid, Relief and Economic Security Act, which passed in spring 2020 to address the myriad threats posed by the coronavirus pandemic, including the risk to people living and working in overcrowded prisons.

But in January, five days before President Biden took office, the Justice Department’s Office of Legal Counsel determined that nearly all those people would need to return to prison once the government said the pandemic no longer constituted an emergency.

Of the approximately 4,800 inmates who were placed on home confinement under the CARES Act, the Justice Department estimated, about 2,800 would have been returned to prison if the coronavirus emergency had ended immediately.

Mr. Garland had personally asked the Office of Legal Counsel to reconsider the opinion, a Justice Department spokeswoman said.

“We will exercise our authority so that those who have made rehabilitative progress and complied with the conditions of home confinement, and who in the interests of justice should be given an opportunity to continue transitioning back to society, are not unnecessarily returned to prison,” Mr. Garland said.

After department lawyers issued a memo on Tuesday that reversed its previous position, the attorney general called inmate advocates to inform them of the decision.

Holly Harris, the president and executive director of Justice Action Network, a bipartisan criminal justice reform group, hailed the reversal.

“The constant threat of returning to prison was so terrible,” she said. “People have gotten jobs and reconnected with their children. The relief they have to be feeling right now is overwhelming.”

The Trump-era memo had created a state of dread for those in home confinement.

“We’d been told over and over that the memo was off-limits and that there was no hope of reversing it,” Ms. Harris said. “But we’d been aware of other memos that had been overturned, and we felt that the administration could do it.”

In a phone call, Mr. Garland told Ms. Harris that the new opinion represented the legally correct conclusion. She said she also believed it was morally correct.

The Office of Legal Counsel said in its new memo that a more accurate reading of the law gave the Bureau of Prisons “discretion to permit prisoners in extended home confinement to remain there.”

Mr. Garland said in a statement that the Justice Department would come up with rules that would ensure that it “lives up to the letter and the spirit of the CARES Act.”

The Justice Department has declined to reverse other high-profile legal decisions that were made under President Donald J. Trump. It continued to keep secret a memo related to how William P. Barr, the former attorney general, considered how to interpret the findings of the special counsel’s report on Russian interference in the 2016 election. The department also chose to continue to defend Mr. Trump in a defamation suit filed by the writer E. Jean Carroll.

But the Justice Department under Mr. Garland has reversed course from the Trump administration on law enforcement and criminal justice issues. Mr. Garland imposed a moratorium on federal executions pending a review of the department’s policies and procedures. And he rescinded a policy that curbed the use of consent decrees to address police misconduct. The department also issued a memo directing law enforcement officers to use body cameras for the first time.