After Election Day, eight states have voted to fully legalize marijuana. Already, four of these states — Alaska, Colorado, Oregon, and Washington — have retail marijuana shops. The other four — California, Maine, Massachusetts, and Nevada — expect to launch their own legal marijuana shops in the next few years.

There’s just one problem: The Trump administration could bring this all to an end — or, at the very least, it could do everything in its power to make legalization very difficult for these and other states.

Even if a state legalizes marijuana under its own laws, pot remains illegal at the federal level. That means the federal government — and particularly the US Department of Justice and Drug Enforcement Administration (DEA) — can still go after state-legal pot shops with the threat of federal law.

The Obama administration has generally taken a hands-off approach to state marijuana legalization, letting states dictate their own marijuana policies as long as they follow a few guidelines (such as not letting legal pot fall into kids’ hands). But if Alabama Sen. Jeff Sessions, Donald Trump’s nominee for attorney general, is approved by the Senate and put in charge of the Justice Department, that could change.

Sessions once said that “good people don’t smoke marijuana.” And he could head the Justice Department.

Sessions has been a big supporter of the war on drugs and critic of legal pot during his time in the Senate. He was one of the few senators who effectively killed a bipartisan criminal justice reform bill this year. At a Senate hearing in April, he said that “we need grown-ups in charge in Washington to say marijuana is not the kind of thing that ought to be legalized, it ought not to be minimized, that it’s in fact a very real danger.” And he declared that “good people don’t smoke marijuana.”

The implication from his record and these types of comments is he thinks the Justice Department should crack down on states’ legalization efforts — something the Obama administration has explicitly avoided doing.

So what would a crackdown look like? The DEA, which falls under the Justice Department, could be freed up to raid state-legal marijuana farms and shops, confiscate these businesses’ product, and shut them down. Federal prosecutors, also under the Justice Department’s supervision, could file and prosecute federal charges against state-legal marijuana businesses, effectively treating them as illicit drug dealers.

If the Justice Department were really serious about this, it could try to shut down every state-legal marijuana business in the country. But even if the Justice Department didn’t go that far, these types of prosecutions could have a chilling effect — signaling to other states that they can’t legalize pot without risking federal enforcement, and perhaps scaring off other businesses from launching their own pot operations in states where marijuana is already legal. At the very least, aggressive action from the Justice Department could stall legalization’s progress until a new administration takes power.

Indeed, this is what some anti-legalization advocates are counting on as surveys show that marijuana legalization is becoming more and more popular with US voters. Sessions “is by far the single most outspoken opponent of marijuana legalization in the US Senate,” Kevin Sabet, head of the anti-legalization group SAM, told the Washington Post. “If I were betting on the prospects for marijuana legalization, I’d be shorting.”

There’s a good chance the Justice Department could ignore marijuana legalization

Still, there’s good reason to believe none of this will happen.

For one, President-elect Donald Trump doesn’t want it to happen. He said on the campaign trail that marijuana legalization should be left to the states.

But the president normally doesn’t micromanage Justice Department policy, treating the Justice Department mostly as a quasi-independent agency. That may be especially true for Trump, who seems largely uninterested in any policy issues except immigration and trade. So it’s possible that Sessions and those under him may carry out their own commands on marijuana legalization.

The question then would be whether Sessions and others at the Justice Department really want to use their time and resources on this issue. Marijuana legalization is very important to activists and Reddit, but it’s not really the most pressing issue in America today — the Trump administration has prioritized immigration and “law and order” issues that have little to do with pot.

Legalization is also very popular: A 2016 Gallup poll found that 60 percent of adults in the US say marijuana should be legal. And the states that have legalized did it through ballot initiatives, proving that this is something these states’ voters want.

So will the Trump administration really be willing to undertake a big enforcement effort against these states’ own laws and risk all the potential backlash that could come from that, potentially drawing attention away from its bigger policy priorities?

It’s an open question. But drug policy reform advocates, for their part, are worried.