In 1970, at the height of his white-hot war on crime, President Richard Nixon demanded that Congress pass the Controlled Substances Act to crack down on drug abuse. During the debate, Senator Thomas Dodd of Connecticut held up a package wrapped in light-green paper that he said contained $3,000 worth of marijuana. This substance, he said, caused such “dreadful hallucinations” in an Army sergeant in Vietnam that he called down a mortar strike on his own troops. A few minutes later, the Senate unanimously passed the bill.

That law, so antique that it uses the spelling “marihuana,” is still on the books, and is the principal reason that possessing the substance in Senator Dodd’s package is considered illegal by the United States government. Changing it wouldn’t even require an act of Congress — the attorney general or the secretary of Health and Human Services could each do so — although the law should be changed to make sure that future administrations could not reimpose the ban.

Repealing it would allow the states to decide whether to permit marijuana use and under what conditions. Nearly three-fourths of them have already begun to do so, liberalizing their laws in defiance of the federal ban. Two have legalized recreational use outright, and if the federal government also recognized the growing public sentiment to legalize and regulate marijuana, that would almost certainly prompt more states to follow along.

The increasing absurdity of the federal government’s position is evident in the text of the Nixon-era law. “Marihuana” is listed in Schedule I of the Controlled Substances Act alongside some of the most dangerous and mind-altering drugs on earth, ranked as high as heroin, LSD and bufotenine, a highly toxic and hallucinogenic toad venom that can cause cardiac arrest. By contrast, cocaine and methamphetamine are a notch down on the government’s rankings, listed in Schedule II.

That illogical distinction shows why many states have begun to disregard the federal government’s archaic rules. Schedule II drugs, while carrying a high potential for abuse, have a legitimate medical use. (Even meth is sold in prescription form for weight loss.) But according to the language of the law, marijuana and the other Schedule I drugs have “no currently accepted medical use in treatment in the United States.”

States Take the Lead No medical use? That would come as news to the millions of people who have found that marijuana helped them through the pain of AIDS, or the nausea and vomiting of chemotherapy, or the seizures of epilepsy. As of this month, 35 states and the District of Columbia permit some form of marijuana consumption for medical purposes. New York is one of the latest states to defy the tired edict of the Controlled Substances Act.

It’s hard for the public to take seriously a law that says marijuana and heroin have exactly the same “high potential for abuse,” since that ignores the vastly more addictive power of narcotics, which have destroyed the lives of millions of people around the world. (There are no documented deaths from a marijuana overdose.) The 44-year refusal of Congress and eight administrations to alter marijuana’s place on Schedule I has made the law a laughingstock, one that states are openly flouting.

In addition to the medical exceptions, 18 states and the District of Columbia have decriminalized marijuana, generally meaning that possession of small amounts is treated like a traffic ticket or ignored. Two states, Colorado and Washington, have gone even further and legalized it for recreational purposes; two others, Alaska and Oregon, will decide whether to do the same later this year.

The states are taking the lead because they’re weary of locking up thousands of their own citizens for possessing a substance that has less potential for abuse and destructive behavior than alcohol. A decision about what kinds of substances to permit, and under what conditions, belongs in the purview of the states, as alcohol is handled.