Lucy Nicholson / Reuters

When Attorney General Jeff Sessions issued a memo on marijuana to federal prosectors Thursday, reiterating their leeway to prosecute federal marijuana laws as they see fit, regardless of whether the plant is legal under state and local law, he likely spurred future infringements on liberty, struck a blow against federalism, and defied public opinion. But he also acted in a manner consistent with the rule of law as it has been clearly interpreted by the U.S. Supreme Court.

To defang the prohibitionism that Sessions has a legal right to advance—and that rescinds what some saw as an overstep of executive authority by his predecessors in the Obama administration, who urged federal prosecutors to hold back from enforcing pot laws in some states—Congress must repeal federal statutes, returning marijuana policy and regulation to the states where it belongs.

Reforms in the War on Drugs of that sort are long overdue.

Since 1970, the federal government has paid men with guns to cage human beings for growing, possessing, or selling the popular marijuana plant. But over time, public opinion has turned against that morally dubious assault on human freedom: The people of 29 states, the District of Columbia, Puerto Rico, and Guam have passed laws allowing the use of the plant for medicinal purposes, while the people of eight states have legalized the recreational use of marijuana, even as the federal prohibition against the drug remains in effect.

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.”

With more than half of states running afoul of the marijuana provisions of the Controlled Substances Act, you’d think a Senate bill to amend it would pass easily; given how populous the marijuana-friendly states are compared to the prohibitionist states, you’d think a House bill could pass, too. For heaven’s sake, President Trump said during the 2016 campaign that the matter should be left to the states. But whether due to cowardice, the fact that Congress is so much more elderly than the population it represents on this generationally divided issue, or some other factor, the unpopular federal policy remains in effect.

Among those in the Senate who’ve championed the federalist position, some with regard to medical marijuana and some encompassing even recreational use: Senators Cory Booker, Kirsten Gillibrand, Rand Paul, Lisa Murkowski, and Mike Lee.

As Cooke put it at National Review, “If Colorado or Oregon want to legalize weed while Mississippi and Utah ban it, that’s fine. In fact, that is how the country is supposed to work. The United States is a collection of … well, of states; it is not a giant centralized democracy with fifty regional departments. Congress should make it a priority to get the federal government out of this area, and to let the states, not the attorney general’s fealty, determine which rules are best for their citizenries. And conservatives, of all people, should celebrate that. The Founders did not write the Constitution to impose uniformity on hemp. Rarely will we get a better teaching moment than this one.”

But for now, the conservative attorney general in a Republican administration is thwarting federalism, the Tenth Amendment, and an exercise of liberty that the states are advancing. May history remember him as the last federal attorney general to preside over the moral abomination that is America’s federal war on pot.

This article is part of our project “The Presence of Justice,” which is supported by a grant from the John D. and Catherine T. MacArthur Foundation’s Safety and Justice Challenge.

We want to hear what you think. Submit a letter to the editor or write to letters@theatlantic.com.