Those state efforts are in keeping with the text of the Tenth Amendment, which declares, “The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.” But they run afoul of a long series of court decisions that warped the Constitution so sweepingly that by 2005, the Supreme Court was declaring that the delegated power “to regulate interstate commerce” somehow allowed Congress to criminalize a cancer patient growing pot in their own garden for personal use, even in states where the substance was legal. “By holding that Congress may regulate activity that is neither interstate nor commerce under the Interstate Commerce Clause,” the conservative Supreme Court Justice Clarence Thomas observed in his dissent, “the Court abandons any attempt to enforce the Constitution's limits on federal power."

Broadly speaking, progressives have cheered absurdist expansions of the commerce clause and the erasure of states rights, while conservatives have urged a recovery of the clause’s original meaning and championed the Tenth Amendment, even to excess, as when states’ rights were cited to oppose civil-rights laws.

But drug policy has made hypocrites of both sides.

Even many progressives who’ve otherwise treated states’ rights as a simple code for racism have been very supportive of efforts, most popular in blue states, to legalize or decriminalize marijuana; and even many older conservatives who cheered Barry Goldwater and William F. Buckley even in their wrongheaded, states’ rights-based opposition to civil-rights laws have always wanted the feds to keep investigating, prosecuting, and caging people caught with weed.

The reefer madness afflicting prohibitionists of all stripes is unpopular.

“Americans continue to warm to legalizing marijuana, with 64 percent now saying its use should be made legal,” Gallup noted a few months ago. “This is the highest level of public support Gallup has found for the proposal in nearly a half-century.”

Nevertheless, Congress has so far declined to let states decide. On Thursday, Senator Cory Gardner, a Republican from Colorado, one of the first states to legalize marijuana for recreational use, declared on Twitter, “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. 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.”

The commentator Charles C.W. Cooke wrote in response, “As a proponent of robust federalism and opponent of the Drug War in toto, I agree with Gardner on the substance, but it’s beyond preposterous that our legislators perpetuate this incessant focus on the executive when they are the ones who write the law. We’ve reached a point at which senators are threatening to understaff the executive if the executive doesn’t decline to enforce the laws over which senators have control.”