Attorney General Jeff Sessions has rescinded several Obama-era directives that discouraged enforcement of federal marijuana laws in states that had legalized the substance.

In a memo sent to U.S. attorneys Thursday, Sessions noted that federal law prohibits the possession and sale of marijuana, and he undid several previous Obama administration memos that advised against bringing weed prosecutions in states where it was legal to use for recreational or medical purposes. Sessions said prosecutors should use their own discretion — taking into consideration the department’s limited resources, the seriousness of the crime, and the deterrent effect that they could impose — in weighing whether charges were appropriate.

“It is the mission of the Department of Justice to enforce the laws of the United States, and the previous issuance of guidance undermines the rule of law and the ability of our local, state, tribal, and federal law enforcement partners to carry out this mission,” Sessions said in a statement. “Therefore, today’s memo on federal marijuana enforcement simply directs all U.S. Attorneys to use previously established prosecutorial principles that provide them all the necessary tools to disrupt criminal organizations, tackle the growing drug crisis, and thwart violent crime across our country.”

The move, first reported by the Associated Press , potentially paves the way for the federal government to crack down on the burgeoning pot industry — though the precise impact remains to be seen, the Washington Post reports.