Former U.S. attorneys are in shock over Attorney General Jeff Sessions' latest hard-line shift on criminal justice.

The head of the Justice Department issued a sweeping new policy change on Friday, ordering all federal prosecutors to pursue the strictest charges and sentences in criminal cases. The move is an effort by Sessions to crack down on drug use and violent crime in order to bolster public safety.

Brett Tolman, former U.S. Attorney for the District of Utah, is confused why Sessions is ignoring "decades of data that shows us that we can't prosecute our way out of the drug problem."

States have been successful in reducing incarceration and keeping the streets safe, Tolman says. Now, the federal government is "ignoring states that have figured it out."

"It flies in the face of what we've learned […] It's very difficult to accept," Tolman, who worked for both the administrations of former Presidents George W. Bush and Barack Obama, told the Washington Examiner.

In South Carolina for example, sentencing reforms have saved the state an estimated $491 million, in addition to reducing incarceration times for nonviolent offenders and helping the crime rate drop. The reduction in incarceration has actually caused six prisons to close.

"We are putting in place a policy that is going to do more harm to the budget, to recidivism and the crime rate," Tolman told the Washington Examiner.

For Tim Heaphy, it is frustrating to see Sessions reversing years of hard work to reform the criminal justice system.

"It's another bad decision [by Sessions]," the former U.S. Attorney for the Western District of Virginia said in a phone interview.

Heaphy, who was in office from 2009 to 2015 after being appointed by Obama, says the Justice Department, under Attorney General Eric Holder, "worked really hard […] to tailor outcomes" for the sentences for low-level offenders.

"This is a return to the war on drugs that led to mass incarceration. It's expensive and ineffective," he said. Heaphy said he questions where the "dollars come from" for more federal cases.

Trump's proposed 2018 budget for the Justice Department is $27.7 billion — a 4 percent decrease from the 2017 fiscal budget. The proposal reflects Sessions' tough-on-crime priority, giving the FBI more money and enhancing border security and immigration programs. However, the department does want to slash roughly $700 million in unnamed "outdated programs," and also cut $1 billion in federal prison construction spending — something that could be an issue if Sessions' memo sends more people behind bars.

"This does not seem like the wise use of federal resources," Heaphy said of the memo.

Tim Purdon is confused why Sessions would attack something that has bipartisan support on Capitol Hill. The former U.S. attorney for the District of North Dakota is referring to the Sentencing Reform and Corrections Act of 2015, which had bipartisan support from not just Democrats and Republicans last year, but Obama as well.

"For the past two or three years, you've really had — one of the few issues that people agreed upon was the need for comprehensive criminal justice reform. This is not the sort of reform that AG Sessions is recommending [with the memo]," Purdon told Washington Examiner.

"He's taking a step backwards," Purdon added. "People are looking for a solution that doesn't build the prison population. We can't afford the prisons we've got right now, and this is not going to solve that problem."

There are roughly 2.2 million people in both jails and prisons nationwide, according to the Sentencing Project. America's incarceration rate is one that constantly makes headlines as being disproportional to the population.

However, since 2010, the federal prison population has dropped both overall and for people serving time for drug offenses. In 2010, roughly 98,000 people were in federal prison for drug offenses; that number fell to 92,000 in 2015.

The Sentencing Project's executive director is concerned that Sessions' memo will raise the prison population again.

"Reversing this directive will exacerbate prison overcrowding, increase spending and jeopardize the safety of staff and prisoners," Marc Mauer said. "Research over many decades has demonstrated the deterrent effect of the criminal justice system is a function of the certainty of punishment, not its severity. The new policy shift will have little impact on public safety, while adding exorbitant fiscal and human costs to an already bloated and destructive criminal justice system."