Sen. Cory Gardner, R-Colo., vowed to block any of President Trump's nominations for the Justice Department if Attorney General Jeff Sessions rescinds an Obama-era policy that allowed legal marijuana use in some states to flourish.

"This reported action directly contradicts what Attorney General Sessions told me prior to his confirmation. With no prior notice to Congress, the Justice Department has trampled on the will of the voters in CO and other states," Gardner tweeted Thursday morning.

"I am prepared to take all steps necessary, including holding DOJ nominees, until the Attorney General lives up to the commitment he made to me prior to his confirmation," he added.

Gardner, who represents a state where marijuana sales and possession are legal, reminded Trump of his former position that the legalization of marijuana ought to be decided by the states, not the federal government, following the Justice Department's forthcoming decision to rescind the Obama administration's Cole Memo. That guidance directed federal prosecutors to evaluate marijuana prosecutions on a case-by-case basis in states where marijuana was legalized by voters, and mainly led to federal authorities standing down and allowing personal use of marijuana to grow.

He also shared a video of a reporter asking Trump in July 2016 if he supported the idea of using federal authority to shut down the recreational sale of marijuana in the states.

"I wouldn’t do that, no. I think it should be up to the states, absolutely," Trump said in 2016.

Gardner tweeted Thursday morning, "@realDonaldTrump had it right. This must be left up to the states."

Two people told the Associated Press Thursday morning that Attorney General Jeff Sessions is expected to allow federal prosecutors based in jurisdictions where pot is legal to decide how seriously they will enforce those federal laws, which are superior to state laws.