The Justice Department will once again use private prisons to house federal inmates, reversing an Obama-era directive to stop using the facilities, which officials had deemed less safe and less effective than those run by the government.

In a one-paragraph memo, Attorney General Jeff Sessions rescinded the previous directive to the Bureau of Prisons to either reduce or decline to renew private-prison contracts as they came due.

“The memorandum changed long-standing policy and practice, and impaired the bureau’s ability to meet the future needs of the federal correctional system,” Sessions wrote.

“Therefore, I direct the bureau to return to its previous approach.”

The directive marks a significant policy shift from the previous administration, although the practical impact might be somewhat muted.

Most inmates are housed in state prisons, rather than federal ones. Even when the Justice Department announced it would no longer use private facilities, the action only affected 13 prisons, housing a little more than 22,000 inmates.

The original directive also did not apply to Immigration and Customs Enforcement and U.S. Marshals Service detainees, who are technically in the federal system but not under the purview of the federal Bureau of Prisons.

Private-prison operators already stood to benefit substantially from President Trump’s aggressive measures to detain and deport illegal immigrants.

As of Thursday afternoon, the Bureau of Prisons had 12 privately run facilities, holding 21,366 inmates. They are run by three private-prison operators: Management and Training Corporation, the GEO Group and CoreCivic, which used to be known as the Corrections Corporation of America.

Private prisons have faced significant criticism in recent years from civil liberties advocates and others.

Sally Yates, who served as deputy attorney general in the Obama administration, did not mince words in August when she ordered the Department of Justice – of which the Bureau of Prisons is a part – to end the use of private prisons entirely by phasing them out over time.

“They simply do not provide the same level of correctional services, programs, and resources; they do not save substantially on costs; and as noted in a recent report by the Department’s Office of Inspector General, they do not maintain the same level of safety and security,” Yates wrote.

The inspector general’s report concluded, among other things, that privately operated facilities incurred more safety and security incidents than those run by the federal Bureau of Prisons.

Private-prison operators vigorously disputed that report’s conclusions, and they hailed Thursday’s memo from Sessions as vindication.

Jonathan Burns, a CoreCivic spokesman, said the announcement “validates our position that the department’s previous direction was not reflective of the high quality services we have provided to the federal government for decades.”

Pablo Paez, a spokesman for the GEO Group, said the company believed the Justice Department’s earlier decision was “based on a misrepresentation,” and it welcomed the reinstatement of “long-standing practice and policy at the federal level.”

Issa Arnita, a spokesman for Management and Training Corp., said the new directive empowers the Bureau of Prisons “to manage its facilities in a way that provides the greatest value to taxpayers and the inmates in their care.”