DENVER (AP) — President Donald Trump has promised to support legislation protecting the marijuana industry in states that have legalized the drug, a move that could lift a threat to the industry made by the U.S. attorney general just three months ago.

Republican Sen. Cory Gardner of Colorado said Friday that Trump made the pledge to him in a Wednesday night conversation.

It marked the latest flip by the president who pledged while he was campaigning to respect states that legalized marijuana but also criticized legalization and implied it should be stopped.

Gardner has been pushing to reverse a decision made by Attorney General Jeff Sessions in January that removed prohibitions that kept federal prosecutors from pursuing cases against people who were following pot laws in states such as Colorado that have legalized the drug.

Marijuana has been fully legalized in eight states, and 24 states allow some form of marijuana use.

"President Trump has assured me that he will support a federalism-based legislative solution to fix this states' rights issue once and for all," Gardner said in a statement.

White House spokeswoman Sarah Huckabee Sanders said Gardner's account was accurate and the president supported states' rights in the matter.

Gardner hopes to introduce bipartisan legislation keeping the federal government from interfering in state marijuana markets.

Marijuana legalization advocates were ebullient.

"We may now be seeing the light at the end of the tunnel," said Mason Tvert, who spearheaded the 2012 ballot measure legalizing recreational marijuana in Colorado. "This is one more step toward ending the irrational policy of marijuana prohibition, not only in Colorado but throughout the country."

Other marijuana supporters were wary given the president's record of reversing positions and pledges of legislative support.

"This cannot be another episode of @realDonaldTrump telling somebody whatever they want to hear, only to change directions later on," U.S. Sen. Ron Wyden of Oregon, a Democrat, wrote on Twitter.

Opponents of legalization said they were concerned. "We hope the president — who doesn't want to be known as the 'Pot President' — will reverse course soon," said Kevin Sabet, founder of Smart Approaches to Marijuana. "This reckless plan will not go unanswered."

During his campaign, Trump said states should be able to chart their own course on marijuana. "I'm a states person, it should be up to the states, absolutely," he told one television interviewer in Colorado in 2016.

However, at the Conservative Political Action Conference in 2015, Trump said he supported medical marijuana but called recreational pot "bad."

He singled out Colorado, the first state in the nation to allow recreational marijuana sales. "They've got a lot of problems going on right now in Colorado – some big problems," Trump told the crowd.

When he selected Sessions, a former federal prosecutor and U.S. senator from Alabama, as his attorney general, marijuana supporters girded themselves for a crackdown. But Gardner said Sessions had promised him he'd do nothing to interfere with Colorado's robust marijuana market.

Gardner said he was blindsided when Sessions made his announcement in January regarding pot prosecutions.

In retaliation, Gardner used his power as a senator to prevent consideration of any nominees for the Department of Justice — an extraordinary step for a senator to use against an administration run by another member of his party.

Some of Gardner's fellow GOP senators groused at the impact of the hold, and Gardner allowed some nominees to proceed in a "good-faith" gesture last month. On Friday, he said he was fully releasing his holds on Department of Justice nominations.

The action came amid widespread speculation that Trump will remove Justice officials overseeing the Russia investigation. Replacements of any of those officials would require new nominations.

Gardner and the Department of Justice have been in discussions for months to get the holds lifted. Gardner has met with Sessions and Deputy Attorney General Rod Rosenstein, the official overseeing the Russia probe who has been the target of Trump's ire.

Legislation to protect states where marijuana is legal is still being drafted.

It may be modeled on a 2014 budget amendment that prevented the Department of Justice from spending money to enforce federal laws against marijuana users and businesses in states that legalized the drug and were following all applicable state laws.

Gardner's office is hopeful of getting enough bipartisan support for the bill to pass the GOP-controlled Congress — something the president's backing would aid.—NICHOLAS RICCARDI (AP)

AP writer Jill Colvin in Washington contributed to this report