Jeff Sessions’ selection as attorney general, announced Friday, could be a setback to the burgeoning movement to legalize marijuana.

The Alabama Republican, who declared at an April Senate hearing that “good people don’t smoke marijuana,” is one of Congress’s staunchest opponents of legalization.

“This should put the brakes on marijuana investments and further plans to legalize until there is more clarity,” said Kevin Sabet, co-founder of Smart Approaches to Marijuana, an organization that compiles arguments against legalization. “I’d think marijuana investors — and legalizers — might be rethinking their strategy right now.”

Legalization advocates warned that any anti-legalization action would cause “huge political problems.”

“The truth is, marijuana reform is much more popular with voters than most politicians are, and officials in the new administration would do well to take a careful look at the polling data on this issue before deciding what to do,” said Tom Angell, founder of the advocacy group Marijuana Majority.

As the top law enforcement officer of the federal government, Sessions’ job would be to carry out the Trump administration’s policies, not set his own. His appointment is subject to confirmation in the Senate.

Incumbent Attorney General Loretta Lynch, for example, has stated that she is against marijuana legalization. But the Justice Department has followed Obama administration policies that have allowed state-sanctioned businesses to operate, even though they are technically violating federal laws.

But with Trump, so far, offering little indication of his position on the issue, Sessions could be in a position to influence the direction the president-elect decides to take, said John Hudak, a senior fellow at the Brookings Institution who writes about drug policy.

“If Trump wants marijuana policy to look a certain way, it will look that way,” Hudak said. “That assumes that president Trump cares about marijuana policy.”

Trump has said he supports medical marijuana. He made conflicting statements about full legalization during his campaign but said he would respect state laws.

Both the House and Senate have voted since 2014 to prohibit the Justice Department from using federal money to prosecute medical marijuana businesses in states where it is legal. That prohibition, an amendment to an appropriations bill, must be re-approved every Congress.

The attorney general’s office could file lawsuits against states that are setting up regulatory systems. It could also repeal a landmark 2013 Obama administration policy that stated the DOJ would largely defer to states to enforce marijuana laws.

Recent polls have shown a majority of Americans support legalization, including October polls by Gallup and Pew that found 60 percent and 57 percent in favor respectively.

“Voters in 28 states have chosen programs that shift cannabis from the criminal market to highly regulated, tax-paying businesses,” Aaron Smith, the executive director of the National Cannabis Industry Association, said in a statement. “Sen. Sessions has long advocated for state sovereignty, and we look forward to working with him to ensure that states’ rights and voter choices on cannabis are respected.”

Voters in California, Maine, Massachusetts and Nevada approved marijuana for recreational use on Election Day, although a recount has been requested in Maine. Florida, North Dakota, and Arkansas approved medical marijuana initiatives. And voters in in Montana rolled back restrictions on an existing medical marijuana law.

Arizona voters narrowly rejected a ballot initiative that would have legalized recreational use.