Attorney General Jeff Sessions sparked a freakout among marijuana supporters on Thursday by rescinding a policy memo of his predecessor — but former prosecutors maintained the move likely will not drastically affect the burgeoning recreational pot business.

Joseph diGenova, who served as U.S. attorney for the District of Columbia in the 1980s when Sessions had the same position in Mobile, Alabama, noted that federal prosecutors would retain discretion over what cases to bring.

“Not much is going to change except the policy,” he predicted.

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James Cole, a deputy attorney general under Attorney General Eric Holder, wrote a memo in 2011 directing the Justice Department to take a hands-off approach to businesses licensed under state laws legalizing the drug. That approach applied as long as states tried to stop people from taking marijuana to jurisdictions where it was still illegal and prevented children from buying it.

In rescinding that policy, Sessions instructed U.S. attorneys to enforce the laws enacted by Congress. He said in a statement that the Holder-era guidelines undermined “the rule of law and the ability of our local, state, tribal, and federal law enforcement partners to carry out this mission” of fighting illegal drugs.

“Therefore, today’s memo on federal marijuana enforcement simply directs all U.S. attorneys to use previously established prosecutorial principles that provide them all the necessary tools to disrupt criminal organizations, tackle the growing drug crisis, and thwart violent crime across our country,” he stated.

The decision provoked outrage — particularly among politicians in states that have legalized marijuana sales.

Rep. Ted Lieu (D-Calif.) tweeted this: “A list of things more important for federal prosecutors and federal law enforcement to pursue other than marijuana: 1. Basically anything.”

Rep. Earl Blumenauer (D-Ore.) tweeted that it was “outrageous” and “perhaps one of the stupidest decisions the attorney general has made.”

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Sen. Cory Gardner (R-Colo.) tweeted that the attorney general’s action contradicts what Sessions told him prior to his confirmation. “I am prepared to take all steps necessary, including holding DOJ nominees, until the attorney general lives up to the commitment he made to me prior to his confirmation,” he tweeted.

Rep. Ted Lieu (D-Calif.) tweeted: “A list of things more important for federal prosecutors and federal law enforcement to pursue other than marijuana: 1. Basically anything.”

And Sen. Rand Paul (R-Ky.) said on “The Laura Ingraham Show” Thursday that the federal government ought to let states pave their own way on marijuana. “I think it’s a mistake for the Department of Justice to do this. But it will be virtually impossible. They would have to send an army in federal troops in there.”

DiGenova said an army of federal troops is unlikely. He predicted federal prosecutors will focus limited resources on marijuana trafficking by criminal organizations.

“There is going to be a black market,” he said. “Because of taxation and the cost of packaging and quality control, there will be a very, very large black market.”

The National Association of Assistant United States Attorneys, which represents career prosecutors in the federal system, indicated that decisions about whether marijuana should be legal or not are best answered by Congress.

“The enforcement of our current laws regarding marijuana should be treated no differently than any other federal statute that AUSAs are obligated to enforce,” the group said in a statement. It added that resources and priorities set by U.S. attorneys and the attorney general always should be considered.

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William Otis, who served as an assistant U.S. attorney for 18 years, said he views the change as a restoration of long-standing department policy — and another indication that the true concern of liberals about Sessions was not that he would ignore the law but that he would enforce it.

“That’s their major complaint against him, with great irony,” he said.

But Otis, who contributes to the Crime and Consequences blog and teaches at Georgetown University Law Center, said the change probably will not impact marijuana businesses operating with the blessing of state governments.

“This change on guidance actually is going to make very little difference,” he said. “It’s quite nuanced … It’s a change in emphasis.”

“Everything is on the table.” Luke Niforatos, chief of staff at Smart Approaches to Marijuana, a nonprofit, education-focused group based in Alexandria, Virginia, called the attorney general’s action “a victory for families, communities and youth across the country.”

Niforatos said “everything is on the table” as far as prosecutorial targets.

But diGenova said prosecuting a business or person engaged in marijuana commerce endorsed by a state would be extremely difficult. “It’s an almost impossible case to bring in federal court, because even though it’s illegal, juries are just not going to convict,” he said.

Even if U.S. attorneys decide not to take on marijuana businesses directly, Thursday’s action by Sessions probably will cause investment in the industry to dry up, Niforatos said.

“We believe that is nothing but good … We don’t want to see this industry grow into a multibillion dollar Big Tobacco 2.0,” he said.

Aaron Herzberg, a lawyer and entrepreneur specializing in California’s newly legal cannabis industry, said in a statement that Sessions put the industry in a “precarious position.” But he downplayed the likelihood that the federal government would attempt a full-scale crackdown on the industry.

Herzberg noted that state-run medical marijuana programs are safe under an amendment named for Blumenauer and Rep. Dana Rohrabacher (R-Calif.). Although it is set to expire January 19, he indicated he is cautiously optimistic that Congress will renew it.

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Herzberg wrote that “this multibillion dollar industry is now too big to be shut down by the federal government — the legalization train has left the station.”

If Congress does not want Sessions to enforce marijuana laws, diGenova said, lawmakers should change the law.

“Let’s see if they do that. This will force them to confront the issue,” he said. “The Democrats got used to a Justice Department under Holder and [Loretta] Lynch, which was politically corrupt.”

Otis said that even if rescinding the Cole memo will have little practical effect, it was the right thing to do because the previous directive was a “wink and a nod” that “sent the wrong signal.”

PoliZette senior writer Brendan Kirby can be reached at [email protected]. Follow him on Twitter.