The U.S. Justice Department on Thursday will rescind a marijuana policy begun under Democratic former President Barack Obama that eased enforcement of federal laws as a growing number of states and localities legalized the drug, a source familiar with the matter said.

The Obama-era policy, outlined in 2013 by then-Deputy Attorney General James Cole, recognized marijuana as a “dangerous drug,” but said the department expected states and localities that authorized various uses of the drug to effectively regulate and police it.

Going forward, federal prosecutors around the country will have deference to enforce U.S. laws on marijuana as they see fit in their own districts, added the source, speaking on condition of anonymity.

The upcoming policy change comes just days after California formally launched the world’s largest regulated commercial market for recreational marijuana.

Besides California, other states that permit the regulated sale of marijuana for recreational use include Colorado, Washington, Oregon, Alaska and Nevada. Massachusetts and Maine are on track to follow suit later this year.

The policy being reversed had sought to provide more clarity on how prosecutors would enforce federal laws that ban marijuana in states that have legalized it for medicinal or recreational use. Its rescission could sow confusion and potentially hamper efforts to cultivate local marijuana businesses.

U.S. Attorney General Jeff Sessions has made no secret about his disdain for marijuana. He has said the drug is harmful and should not be legalized. He also described marijuana as a gateway drug for opioid addicts.

A task force created under a February 2017 executive order by Trump and comprised of prosecutors and other law enforcement officials was supposed to study marijuana enforcement, along with many other policy areas, and issue recommendations.

Its recommendations were due in July 2017, but the Justice Department has not made public what the task force determined was appropriate for marijuana.

Sessions and some law enforcement officials in states such as Colorado blame legalization for a number of problems, including drug traffickers who have taken advantage of lax marijuana laws to illegally grow and ship the drug across state lines, where it can sell for much more. The decision was a win for marijuana opponents who had been urging Sessions to take action.

“There is no more safe haven with regard to the federal government and marijuana, but it’s also the beginning of the story and not the end,” said Kevin Sabet, president and CEO of Smart Approaches to Marijuana, who was among several anti-marijuana advocates who met with Sessions last month. “This is a victory. It’s going to dry up a lot of the institutional investment that has gone toward marijuana in the last five years.”