Attorney General Jeff Sessions said Thursday he is effectively unleashing the hounds of the federal government on states that allow for the legalized sale of marijuana, ending a hands-off approach by the previous administration and ignoring promises made by his own boss, President Donald Trump.

In a 2016 interview with a local reporter in Colorado, which legalized recreational cannabis five years ago, then-candidate Trump insisted he would not allow his AG to override state law by prosecuting marijuana businesses and growers. “I’m a states person. I think it should be up to the states, absolutely,” he told Brandon Rittiman from Channel 9 News at the time.

Yet officials suggested to reporters Thursday that businesses and growers in legalized states have gotten too comfortable and that the primacy of state law means very little in Washington. Effectively, Sessions has rescinded a 2013 guidance issued by then-Deputy Attorney General Jim Cole that limited prosecutions as along as individuals and businesses were operating under their state’s laws.

“The Cole memo as interpreted created a safe harbor for the marijuana industry to operate in these states. There is a belief that that is inconsistent with what federal law says,” a senior Department of Justice official, speaking on condition of anonymity, told Politico“I can’t sit here and say whether it will or will not lead to more marijuana prosecutions,” the official continued. “We believe U.S. attorneys’ offices should be opened up to bring all of these cases that are necessary to be brought.”

What this does is create an inevitable stand-off over the 10th Amendment rights of seven states and the District of Columbia that have fully legalized cannabis, including California, which officially made pot legal on January 1.

Another 21 states have medical marijuana laws on the books, including red states like Arkansas, which passed its ballot referendum in 2016, and Florida, which put its own measure over the top by a whopping 71 percent at the polls. The tone set by Sessions today puts people in those states on notice as well.

David Kopel, an adjunct professor of constitutional law at the University of Denver and research director of the Independence Institute, said Sessions’ announcement is sending a shock wave across Colorado, which not only changed its laws, but amended its state constitution to legalize pot. As of July, the state had brought in $505 million in cannabis-related taxes and fees since sales officially began in 2014. Altogether, marijuana sales in North America totaled some $6.7 billion in 2016. Before Sessions’ announcement, experts predicted the U.S. market might reach $50 billion by 2026. To say this is an established industry with thousands of people and livelihoods depending on it would be an understatement.

“This is a direct betrayal of President Trump’s campaign promise, which he made in Colorado,” Kopel told TAC on Thursday. He pointed to the chill this would put on businesses, landlords, and particularly banks that are still hesitant to work with cannabis clients, despite the millions of legal dollars changing hands.

While the federal government doesn’t have the resources to go after every business or cultivator, he noted, “It only takes a few prosecutions to destroy the legal industry in a given state. In fact, they don’t even need to convict, they just need to start sending threatening letters to landlords.”

Sessions drew a swift and angry response from Senator Cory Gardner, R-Colo., who said the AG was “trampling the will of the voters.” Gardner suggested Sessions had assured him of a continued “hands-off” approach during the former Alabama senator’s own nomination hearing. He threatened to play hardball, even putting a hold on all DOJ nominees, including Colorado’s interim U.S. Attorney Bob Troyer, if Sessions proceeds down this path.

“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,” Gardner tweeted Thursday.

Republican Senator Lisa Murkowski, whose home state of Alaska has legalized recreational marijuana, also weighed in with a statement, saying Sessions’ announcement—which she had repeatedly warned him against making—was “disruptive to state regimes and regrettable.”

It is not as if this is altogether unexpected. As Senator, Sessions was a classic law-and-order Republican, who since his confirmation as Trump’s AG, has boosted private prisons, reinstated the federal asset forfeiture program, and moved to lengthen drug sentences, all three of which have roiled civil libertarians and criminal justice reformers alike.

Still, former Republican Maryland state delegate Don Murphy, who now works in conservative outreach for the Marijuana Policy Project, said the timing of the AG’s move, presumably sanctioned by Trump, is odd considering the populist wave in favor of decriminalizing marijuana across the country—not only in blue states, but places like Arkansas, the first Bible Belt state to legalize medical marijuana, and with 53 percent of the vote. Today, 29 states have some sort of law allowing for at the very least, medical marijuana. Right now 12 are poised to consider new laws in 2018. New Jersey’s Governor Elect Phil Murphy has pledged to sign legislation legalizing adult recreational use within 100 days of his new term.

“What Jeff Sessions wants to do is roll back all of that. This is a very bad thing and it’s very unnecessary, considering what the president said publicly and that we are dealing with an opioid crisis right now,” Don Murphy, who actually served as a delegate for Trump and volunteered on his campaign, told TAC. “I want the Trump administration to stand by its promises.”

Murphy has been working on getting a federal medical marijuana bill passed since 2000. His legislation has support on both sides of the aisle, he insists, but members who oppose it have kept it from coming to a floor vote. What supporters have achieved is to pass a 2014 rider to the annual spending bill that has prevented federal funds from being used to prosecute medical marijuana cases in states that allow it. However, it is not clear whether the so-called Rohrabacher-Blumenauer amendment will pass in the current spending bill.

If not, that will leave even more people and businesses vulnerable. The Supreme Court, weighing in on this in 2005, ruled six to three in favor of the federal government’s ban superseding state medical marijuana laws. Congress would have to change the law for states to be entirely free of federal intervention. If not, people who have depended on cannabis and cannabis products to ease suffering—whether it be from epileptic seizures and the side effects of chemotherapy, or chronic pain and glaucoma—may soon be at risk. This includes veterans, who have been choosing cannabis over prescription pills to treat symptoms of post traumatic stress disorder (PTSD).

“What I think may happen is people who otherwise kept their heads down are going to have to stand up and speak out,” charged Murphy.

“This needs to be a state choice. The 10th Amendment says what it says,” he said, noting that as a conservative he’s been able to appeal to other Republicans on states’ rights grounds alone. “I had support from members from Kansas, from Utah… not because they were marijuana people but they were 10th Amendment people. Jeff Sessions doesn’t seem to agree with that and I think it’s all going to come to a head soon.”

Kelley Beaucar Vlahos is executive editor of The American Conservative. Follow her on Twitter @Vlahos_at_TAC