The governors of Washington and Rhode Island petitioned the federal government on Wednesday to reclassify marijuana as a drug with accepted medical uses, saying the change is needed so states like theirs, which have decriminalized marijuana for medical purposes, can regulate the safe distribution of the drug without risking federal prosecution.

The move by the governors — Christine Gregoire of Washington, a Democrat, and Lincoln D. Chafee of Rhode Island, an independent who used to be a Republican — injected new political muscle into the debate on the status of marijuana, which has been raging for decades. Their states are among the 16 that now allow medical marijuana, but which have seen efforts to grow and distribute the drug targeted by federal prosecutors.

“The divergence in state and federal law creates a situation where there is no regulated and safe system to supply legitimate patients who may need medical cannabis,” the governors wrote Wednesday to Michele M. Leonhart, the administrator of the Drug Enforcement Administration.

Marijuana is currently classified by the federal government as a Schedule I controlled substance, the same category as heroin and L.S.D. Drugs with that classification, the government says, have a high potential for abuse and “no currently accepted medical use in treatment in the United States.”

The governors want marijuana reclassified as a Schedule II controlled substance, which would put it in the same category as drugs like cocaine, opium and morphine. The federal government says that those drugs have a strong potential for abuse and addiction, but that they also have “some accepted medical use and may be prescribed, administered, or dispensed for medical use.”

Such a classification would allow pharmacies to dispense marijuana, in addition to the marijuana dispensaries that currently operate in a murky legal zone in many states.

“What we have out here on the ground is chaos,” Governor Gregoire said in a telephone interview. “And in the midst of all the chaos we have patients who really either feel like they’re criminals or may be engaged in some criminal activity, and really are legitimate patients who want medicinal marijuana.

“If our people really want medicinal marijuana, then we need to do it right, we need to do it with safety, we need to do it with health in mind, and that’s best done in a process that we know works in this country — and that’s through a pharmacist.”

The state of Washington approved medical marijuana in 1998, with a ballot question that won 60 percent of the vote. But like many states, Washington soon found itself in a legal gray area. The Legislature tried to clarify things last spring, when it passed a law that would have explicitly legalized, regulated and licensed marijuana dispensaries and growers.

But the Justice Department warned the governor that growing and distributing marijuana was still against federal law, and said that “state employees who conducted activities mandated by the Washington legislative proposals would not be immune from liability.” Ms. Gregoire, while sympathetic to the goals of the bill, wound up vetoing much of it.

It was similar on the other side of the country, where Rhode Island had passed a law authorizing state-regulated marijuana dispensaries. This fall Governor Chafee announced that he could not go ahead with the plan because federal prosecutors had warned him that the dispensaries could be the targets of prosecution.

On Wednesday Mr. Chafee said that reclassifying the drug could help many people. “Patients across Rhode Island and across the United States, many of whom are in tremendous pain, stand to experience some relief,” he said in a statement.

Other groups have sought reclassification of marijuana in the past, and as recently as this past June the Drug Enforcement Administration denied a petition to do so, based on a review conducted several years earlier. But Ms. Gregoire and Mr. Chafee said the attitude of the medical community had changed since the federal government last reviewed the issue.

In 2009 the American Medical Association changed its position and called for reviewing the classification of marijuana, saying that the current classification was limiting clinical research.

Ms. Gregoire noted that many doctors believe it makes no sense to place marijuana in a more restricted category than opium and morphine. “People die from overdose of opiates,” she said. “Has anybody died from marijuana?”

– Article from The New York Times.