Attorney General Jeff Sessions issued a memo late Thursday directing federal prosectors to more harshly punish crimes.

In the memo sent to all 94 United States attorneys' offices, Sessions directed federal prosecutors to bring the most "serious, readily approvable offense" charge in all cases moving forward — a major move by the nation's top law enforcement officer signaling that the Department of Justice is serious about being tough on crime.

The "Sessions memo" rolled back a memo issued by then-Attorney General Eric Holder in 2013 that encouraged prosecutors to use their discretion when filing criminal charges — especially in low-level drug offenses and other cases that elicited mandatory minimum sentences.

In his latest memo, Sessions said "charging and sentencing recommendations are crucial responsibilities for any federal prosecutor."

He added that pursuing the harshest punishment possible for a crime with multiple charges is a policy that "affirms our responsibility to enforce the law, and is moral and just."

This policy change returned the Justice Department to operations conducted under Former President George W. Bush, whose attorney general John Ashcroft in 2003 ordered the same thing.

Should a prosecutor not want to pursue the most serious charge, Sessions says he or she must get the decision approved by a supervisor, such as a U.S. attorney or assistant attorney general.

In 2013, Holder wrote that directing prosecutors to pursue the harshest punishment was hurting the country, citing overcrowding in prisons and overspending by taxpayers.

He announced the policy change in a speech, delcaring "too many Americans go to too many prisons for far too long and for no good law enforcement reason."

"[W]idespread incarceration at the federal, state and local levels is both ineffective and unsustainable," he said.

In one of his first initiatives, Sessions has made policy his disagreement with that judgment.

In every major speech since being confirmed as attorney general, the former federal prosecutor has made it clear that public safety and violent crime are intertwined – and his top priorities.

"We do have strong evidence that aggressive prosecutions of federal laws can be effective in combating crime," he wrote in a March 8 memo. "Our department's experience over decades shows these prosecutions can help save lives."

Roughly a week later he addressed law enforcement officials in Richmond, Va., promising that "this country will not go backwards" and his department would "hammer drug dealers and violent felons."

"We have too much of a tolerance for drug use," Sessions said. "We need to say, as Nancy Reagan said, 'Just say no.' There's no excuse for this, it's not recreational. Lives are at stake, and we're not going to worry about being fashionable."

Sessions has been critical of marijuana too, but this memo does not address the drug — which is legalized in 26 states and the District of Columbia in some form — nor does it address the Cole Memo. That 2013 memo limits the federal government's involvement in state laws legalizing the drug for medicinal or recreational use so long as they follow certain criteria.

Sessions' latest memo will impact on the nation's incarceration rate — the epicenter of bipartisan criminal justice reform in the Obama era. The number of Americans incarcerated for drug offenses jumped steadily beginning in 1980 until 2010. But the number of those behind bars for drug offenses fell from 98,000 in 2010 to 92,000 in 2015. There was also a decrease in federal prison population for all offenses over the same period.

As a federal prosector in southern Alabama in the 1980s to early '90s, Sessions had a reputation for aggressively pursuing drug dealers and users. The Brennan Center for Justice reports that drug convictions made up 40 percent of his convictions when he served as U.S. Attorney for the Southern District of Alabama — double the rate of other Alabama federal prosecutors.

And then as a Republican senator, he blocked the Sentencing Reform and Corrections Act in 2016. The bipartisan legislation was not just supported by House Speaker Paul Ryan, R-Wisc., and the Obama administration, but was lead by fellow Republican Sens. Chuck Grassley (Iowa), Mike Lee (Utah) and John Cornyn (Texas).

The Justice Department has a seat on the U.S. Sentencing Commission, an independent agency that develops sentencing guidelines for federal courts.

The American Civil Liberties Union said the new policy will return the country's criminal justice system to a way that has been proven ineffective.

"Jeff Sessions is pushing federal prosecutors to reverse progress and repeat a failed experiment — the War on Drugs — that has devastated the lives and rights of millions of Americans, ripping apart families and communities and setting millions, particularly black people and other people of color, on a vicious cycle of incarceration," said Udi Ofer, director of the ACLU's Campaign for Smart Justice.