Late last week, Attorney General Jeff Sessions sent a policy memo directing the country’s 93 U.S. attorneys to send people to prison for as long as the law allows. The memo rescinds instructions that the Obama administration gave federal prosecutors between 2010 and 2014, a period during which the Justice Department, under the leadership of Attorney General Eric Holder, tried to reduce the number of people serving long sentences in federal prisons.

“[P]rosecutors should charge and pursue the most serious, readily provable offense,” Sessions wrote in the memo. “This policy affirms our responsibility to enforce the law, is moral and just, and produces consistency.” In case there was any ambiguity, he clarified that “the most serious offenses” are the ones that carry the longest prison sentences, including mandatory minimums.

To find out what the Sessions policy means for the federal prison system, and how it will change the decision-making of U.S. attorneys, I called Mona Lynch, a professor of criminology, law, and society at the University of California–Irvine whose 2016 book, Hard Bargains: The Coercive Power of Drug Laws in Federal Court, is about how federal prosecutors use drug laws as weapons during the plea bargaining process.

Our conversation has been edited and condensed for clarity.

Leon Neyfakh: Before we get into what will change because of this memo, can we review what the Obama administration did in terms of giving guidance to federal prosecutors on charging decisions?

Mona Lynch: So, before the Obama administration came in, the policy that federal prosecutors were following was set forth by what’s known as the “Ashcroft memo.” It was issued under the George W. Bush administration, and it said that prosecutors had to always charge the “most serious, readily provable” offenses. [Attorney General] Eric Holder, in 2010, basically rescinded the Ashcroft memo, and signaled to prosecutors that they should also use their own judgment, and that local conditions should matter, and so on. Holder laid that out in the first of three memos that he issued on prosecutorial discretion and charging decisions.

What were the others?

The second memo came in August 2013. It said that prosecutors should not seek mandatory minimums in cases involving low-level defendants. Then the third memo was in 2014, and that one made clear it was inappropriate for prosecutors to use sentencing enhancements as a threat during plea bargaining negotiations.

It sounds like he was simultaneously giving prosecutors more leeway to be lenient and less leeway to be harsh.

With the 2010 memo, what Holder was trying to do was to stop dictating prosecutorial policy from Washington. Ashcroft had been essentially requiring prosecutors to get approval from D.C. whenever they wanted to deviate from the policy of charging the most serious possible offense. That was his way of controlling what happened around the country across all 90-some districts. Holder was restoring some of the local power, and saying to prosecutors: You set your own policies based on what’s important for your districts. He was saying, “We’re not going to micromanage you in terms of how you charge cases and what cases you bring.”

So that was the first policy memo.

Yes. Then the next two memos essentially said, “Don’t use the law in a draconian way. Don’t use this discretion unwisely to threaten people. Even though I’ve given you more freedom, you are not to use sentencing enhancements to induce guilty pleas.”

What effect did the Holder memos have on the kinds of cases federal prosecutors were taking on?

There’s been a drop-off in the number of drug cases across the nation over the course of 10 years or so. I think prosecutors in most districts realized that there’s a lot of state law that can take care of the drug problem in a locality, and therefore they don’t need to jump in and be excessive on drug cases. They’ve realized they can reserve those resources for more serious cases. Sessions is basically turning back the clock on that.

Why does Sessions want to do that so badly?

He is a drug warrior. He just wants to go back to harsher punishments. It flows directly from the role he took as senator, which was to be an obstructionist on the bipartisan effort to pass sentencing reform. And it stems directly from his elevation of Steve Cook, who was the president of the National Association of Assistant U.S. Attorneys, which is a generally conservative subgroup of U.S. attorneys. They worked very closely with Sessions and Arkansas Sen. Tom Cotton in figuring out ways to take down the movement for sentencing reform.

Do you think Sessions believes his policy will reduce drug use and drug trafficking? Does he think making the system less forgiving and scarier is going to dissuade people from engaging in those activities?

I’m uncomfortable speculating about what’s in his mind. But my sense is that he is ideological, and he rejects evidence that doesn’t comport with his beliefs about these things. He just feels very strongly about using criminal punishment and criminal law to its fullest extent against what he views as the most serious threats to our society. It’s a belief system. Based on what he’s said, he seems to believe that overzealous federal intervention in drug cases is going to create safety. It’s not based on any empirical analysis of how best to spend resources on dealing with a) the problem of drug trafficking and b) the problem of drug use and abuse.

Aside from putting more people in federal prison for drug crimes on longer sentences, what does Sessions’ preoccupation with drugs mean for the kinds of cases prosecutors will pursue?

It means resources won’t go to other issues that the federal government might tackle—things like complex fraud cases and financial crimes that cut across and affect large swaths of people.

Am I right to think that a lot of federal prosecutors will welcome the new directive pretty enthusiastically?

It’s likely to be very place-specific—each district has its own local legal culture. In one of the districts where I did my field work, the consensus view was toward a more rehabilitative model, and people welcomed Holder’s taming of more punitive policies. It allowed them to individualize their approach to cases, and to craft outcomes that were appropriate for each one.

What’s an example of a case where a prosecutor wanted to give someone a shorter sentence than they would have if they had charged the “most serious” crime possible?

I talked to an attorney who was managing a case where the defendant was an elderly man who had drugs packed into his wheelchair, but it was enough to get to a mandatory minimum. The prosecutor and the defense attorney agreed that this case was just not a mandatory minimum case, and because the Holder policy had just been released several months earlier, it was easy to say, “OK, under this policy, this makes sense—we won’t charge the weight so we don’t trigger the mandatory minimum. We will figure out a sentence that fits for this man.” The Holder policy allowed them to feel this was a legitimate and just outcome, and not a case of them going around the law.

So then will there be some U.S. attorneys’ offices where the prosecutors feel, as a result of the Sessions memo, like they’re being forced to be more punitive than they think is fair

What I think is going to happen under this policy—and this is just speculation—is that there will be localities that have operated under this less punitive criminal justice ethos. And some of those places are just not going to bring as many drug cases, because if they do, they’ll have to then charge the most readily provable offense, seek all the enhancements, and just put the pedal to the metal. So they’re just not going to bring as many cases. That doesn’t mean the crimes will go unpunished—the cases will likely end up in state court and they’ll be managed locally.

So, in places in the Northeast, you’ll probably see mainly very serious drug cases being brought, because to bring the little ones will amount to throwing the book at people who the local folks might feel don’t deserve it. Whereas in some places in the South, in particular, they may be “unleashed.” They might devote resources to bringing up all these drug cases to federal court, and say, “We’re gonna go out there and set up all these busts and drag people into federal court and hammer them.”

Is there an argument to be made that the new policy is not going to change all that much—that the kinds of drug charges it would cover tend to go through the state system anyway?

This is the John Pfaff argument: that the federal system doesn’t matter as much as the state systems, taken together. I don’t completely agree. Yes, the number of people in federal prison is relatively small compared to the states collectively, but this has been a system that has severely slammed people. As we saw with Obama’s clemency project, hundreds upon hundreds of people are thrown in prison for life without parole just for being drug dealers, rather than for violence or something like that. I think the number of people like that will probably rise, and I think that’s significant. It’s small relative to the states taken together. But if you compare it to any one state, it’s a pretty darn big system. And it’s about to get much more punitive.