Sending marijuana use back into the shadows only propagates the failed policies of a drug war that has contributed to mass incarceration.

Congress needs to finally act to reclassify marijuana and allow states to make the last call on its legalization — eliminating the uncertainty of a possible federal crackdown.

Attorney General Jeff Sessions created more uncertainty last week by rescinding marijuana policies implemented under the Obama administration. The Justice Department guidelines had discouraged federal marijuana prosecutions in the 29 states where it has been legalized for medical or recreational use.

In a memo to the nation’s 93 U.S. attorneys, Sessions said they could now individually decide whether to pursue marijuana cases in their jurisdictions. The policy should be no surprise coming from Sessions, a longtime anti-drug zealot who once said that “good people don’t smoke marijuana.”

Yet President Trump had said on the campaign trail that marijuana should be a state-by-state issue. Some congressional Republicans in states that have legalized marijuana reacted in anger to the policy change, with Sen. Cory Gardner of Colorado vowing to hold up all Justice Department nominations until it is reversed.

Members of Congress have the opportunity to take the issue out of the hands of this administration and future administrations if they find the political will. H.R. 975 would prohibit federal interference in states where marijuana has been legalized for medical or recreational use.

Another bill, H.R. 1227, would eliminate federal marijuana penalties and remove marijuana from being classified as a Schedule I substance. That classification includes heroin as is meant for drugs with a high potential for abuse and no medical use, a designation completely inappropriate for marijuana.

The Obama administration in 2016 rejected a bid to reclassify marijuana, despite evidence of its benefits in treating chronic pain, nausea and other medical