WASHINGTON — Colorado Sen. Cory Gardner slammed Attorney General Jeff Sessions on Thursday morning, saying the decision to end federal policy that let legal marijuana flourish in states where it’s legal, including Colorado, “contradicts” a commitment that was made to him last year.

“This reported action directly contradicts what Attorney General Sessions told me prior to his confirmation,” Gardner wrote on Twitter.

“With no prior notice to Congress, the Justice Department has trampled on the will of the voters in (Colorado) and other states.”

Sessions is expected to announce Thursday that he is rescinding the policy and instead let federal prosecutors where pot is legal decide how aggressively to enforce federal marijuana law.

Recreational marijuana was approved by Colorado voters in 2012 and the first pot sales in the state began on Jan. 1, 2014.

“I am prepared to take all steps necessary, including holding (Department of Justice) nominees, until the attorney general lives up to the commitment he made to me prior to his confirmation,” Gardner said.

Sessions has said marijuana is comparable to heroin and has blamed it for spikes in violence.

In 2013, the Obama administration announced it would not stand in the way of states that legalize marijuana, so long as officials acted to keep it from migrating to places where it remained outlawed, and out of the hands of criminal gangs and children.

Sessions is rescinding that memo, written by then-Deputy Attorney General James M. Cole, which had cleared up some of the uncertainty about how the federal government would respond as states began allowing sales for recreational and medical purposes.

The pot business has since become a sophisticated, multimillion-dollar industry that helps fund schools, educational programs and law enforcement.

Eight states and the District of Columbia have legalized marijuana for recreational use, and California’s sales alone are projected to bring in $1 billion annually in tax revenue within several years.