In a memo to U.S. attorney's offices released Friday morning, U.S. Attorney General Jeff Sessions ordered federal prosecutors to seek the toughest charges and maximum possible sentences available, reversing an Obama-era policy that sought to avoid mandatory minimum sentences for certain low-level drug crimes.

While the two-page directive leaves some discretion for prosecutors to avoid federal sentencing guidelines, the overall message is clear: Federal prosecutors have the green light to go hard after any and all drug offenses. "It is a core principle that prosecutors should charge and pursue the most serious, readily provable offense," Sessions wrote in the memo.

"We are returning to the enforcement of the laws as passed by Congress, plain and simple," Sessions said in a speech Friday. "If you are a drug trafficker, we will not look the other way, we will not be willfully blind to your misconduct."

The shift marks the first significant return by the Trump administration to the drug war policies that the Obama administration tried to moderate. In 2013, former Attorney General Eric Holder ordered federal prosecutors to avoid charging certain low-level offenders with drug charges that triggered long mandatory sentences.

The federal prison population dropped for the first time in three decades in 2014, and has continued to fall since, although the Bureau of Prisons is still operating at over its rated capacity.

In a statement released Friday, Holder sharply criticized the new policy, saying it would "take the nation back to a discredited past" and put the Justice Department "back on track to again spending one third of its budget on incarcerating people, rather than preventing, detecting, or investigating crime."

"The policy announced today is not tough on crime," Holder said. "It's an ideologically motivated, cookie-cutter approach that has only been proven to generate unfairly long sentences that are often applied indiscriminately and do little to achieve long-term public safety."

The announcement also drew instant condemnation from criminal justice and civil liberties groups, such as the American Civil Liberties Union, the Brennan Center for Justice, Human Rights Watch, and the National Association of Criminal Defense Lawyers.

In a statement, Families Against Mandatory Minimums (FAMM), a nonprofit that works to repeal mandatory minimum sentencing laws, said it was "gravely disappointed" in Sessions' memo.

"While we appreciate the attorney general's commitment to reducing crime and combating dangerous opioid abuse, we think his strategy is misguided, unsupported by evidence, and likely to do more harm than good," FAMM said. "Indeed, the drug epidemic challenging our country today is a devastating indictment of the one-size-fits-all punishment regime that General Sessions seeks to expand. His charging memo throws decades of improved techniques and technologies out of the window in favor of a failed approach."

For an example of what that one-size-fits-all approach looks like, take one of FAMM's most infamous cases: Weldon Angelos was arrested in 2002 for selling marijuana to an undercover officer on three separate occasions. Angelos was carrying a firearm during one of those transactions, although he never displayed or brandished it, which triggered an automatic sentencing enhancement under federal mandatory minimum guidelines. Despite it being Angelos' first drug offense, the judge in his case had no choice but to sentence him to 55 years in prison. Angelos was 23. He was freed after 13 years in prison last year under an arrangement with U.S. Attorneys. Under less stringent guidelines, a thoughtful prosecutor could have looked at Angelos' case and decided not to push for the sentencing enhancements that added decades to Angelos' prison time.

But thoughtful prosecutors and discretion aren't going to happen under Sessions' new guidance. Instead, we'll get more cases like Angelos, more cases like the thousands of nonviolent drug offenders who received commutations under Obama (and the thousands more who were denied clemency because of dysfunction in the White House and pressure from recalcitrant prosecutors).

While it's easy to point the finger at Sessions, though, Congress ultimately passed the laws the Justice Department is tasked with enforcing. Lawmakers in Congress had a golden window of opportunity over the past three years to revise federal sentencing laws—with bipartisan winds at their back and a friendly administration in White House—and failed miserably. Senate Majority Leader Mitch McConnell wouldn't bring a reform bill to the Senate floor, despite significant compromises to assuage tough-on-crime Republicans like Tom Cotton (R-AR). House leadership, meanwhile, waited for the Senate to move before it brought up a slate of criminal justice bills that had passed out of the House Judiciary Committee. Which of course it never did.

Sessions' policy change drew rebukes from some Republicans in Congress who support criminal justice reform.

"Mandatory minimum sentences have unfairly and disproportionately incarcerated too many minorities for too long," Sen. Rand Paul (R-KY) said in a statement. "Attorney General Sessions' new policy will accentuate that injustice. Instead, we should treat our nation's drug epidemic as a health crisis and less as a 'lock 'em up and throw away the key' problem."

Sen. Mike Lee (R-UT), although he did not directly criticize Sessions, wrote in a tweet Friday morning that "to be tough on crime we have to be smart on crime. That is why criminal justice reform is a conservative issue." Lee has been one of the leading GOP lawmakers pushing for criminal justice reform after being elected to the Senate in 2010. He became a staunch reform advocate, coincidentally, after witnessing Weldon Angelos' case as an assistant U.S. attorney.

One of Angelos' other biggest supporters was Mark Holden, the chairman of Freedom Partners Chamber of Commerce. In a statement, Holden, speaking for Freedom Partners, says "we favor a different approach which requires changing some of the existing federal laws."

"Fortunately, there are already federal reform bills from last year that have broad bipartisan support that will address this issue," Holden says. "These reforms are consistent with those enacted by many states the past 10 years. The states have proven that communities and law enforcement are safer when the punishment fits the crime through sentencing reforms. There are less costly and more effective ways to help low level offenders who aren't a threat to public safety other than incarceration. This is also an issue that receives overwhelming public support from across the political spectrum. In one recent poll, 81 percent of voters who supported President Trump described criminal justice reform as in important priority."

Say, if you're intersted in the power of prosecutors, you should register to attend Reason's upcoming panel discussion on the subject, featuring Fordham University law professor John Pfaff, author of Locked in: The True Causes of Mass Incarceration and How to Achieve Real Reform; Ken White, a criminal defense attorney and former federal prosecutor whom you probably know better as Popehat; and the Reason Foundation's director of criminal justice reform, Lauren Krisai. The event is on May 25 at Reason's D.C. office.