WASHINGTON – In the eyes of former President Barack Obama’s Justice Department, private prisons were a sort-of necessary evil – less safe and effective than facilities run by the government, but needed because of the volume of inmates in the federal system. When Deputy Attorney General Sally Yates ordered them to be phased out in favor of government-run facilities last year, she said she was able to do so only because the inmate population had declined, thanks to sentencing reform and other measures to keep people from serving long prison terms.

Attorney General Jeff Sessions sees things differently. As one of his first major acts leading the Justice Department, Sessions reversed Yates’s directive, proclaiming that not using private prisons “impaired the Bureau’s ability to meet the future needs of the correctional system.”

But even Sessions’s Justice Department has noted the federal inmate population is falling. In a recent White House budget proposal, officials even pointed to the 14 percent drop since 2013 as a reason the Justice Department could nix construction of a planned government-run prison and save more than $1 billion in the process.

So why, then, would they need to keep using private prisons?

David C. Fathi, director of the American Civil Liberties Union’s National Prison Project, said the budget proposal indicated either that “the embrace of private prisons was a purely ideological decision unconnected to any actual need,” or Justice Department officials expected they’d now increase the inmate population – and rely on private prisons to help find the bed space.

“The fact that they are simultaneously acknowledging that the federal prison population is falling and saying that they need private prisons to accommodate future needs seems to me can only be explained by a plan to radically increase the private prison population,” Fathi said. “Otherwise, those two things are just irreconcilable.”

The Bureau of Prisons declined to comment for this story. Justice Department officials, who would speak only on the condition of anonymity because budget discussions are ongoing, said they viewed the private prison directive as separate from whether they should press ahead with construction of a new government-run prison. Because the Bureau of Prisons was down roughly 29,000 inmates from 2013 and 2014, there was no longer a need to build a new high-security facility – a move that would save more than $1 billion. The Justice Department still plans to put into use a different high-security facility, which will cost about $80 million.

But Justice Department leaders felt that they still needed private prisons because the facilities give the Bureau of Prisons “more flexibility in the future if they need bed space,” an official said. The private prisons house mostly low-security illegal immigrants serving sentences for convictions on federal offenses, which is different than the population of the facility that was nixed.

Fathi disputed that private prisons offer more flexibility, noting that contracts can come with guarantees that the Justice Department will fill beds. In Arizona, a contractor threatened to sue when the state had not filled the beds as required by contract.

“The myth of flexibility created by private prisons really is just that, a myth,” Fathi said.

In her memo directing the Justice Department to stop using private prisons, Yates wrote the facilities “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.” Private prison operators vigorously disputed those assertions, even rallying legislators to their side as they tried to persuade the Justice Department to move away from its position. Sessions wrote that ceasing their use “changed long-standing policy and practice.”

The private-prison industry generates billions of dollars each year and gives substantial amounts to politicians. Two private prison operators – the GEO Group and CoreCivic donated $250,000 each to support President Trump’s inaugural festivities, spokesmen for the companies said. Separately, the GEO Group gave $275,000 to the pro-Trump super PAC Rebuilding America Now, according to FEC filings.

While the Justice Department’s previous decision to stop using private prisons was symbolically significant, the practical impact was more limited. At the time of the announcement, the action affected just 13 prisons, housing a little more than 22,000 people. That is because the directive did not apply to 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. Nor did it affect state systems – which house most prisoners in the United States.