As federal battles over medical marijuana across the country heat up, a statement from one federal agency may be a huge asset for medical marijuana dispensaries that have been targeted by the various arms of the U.S. Department of Justice and the IRS.

The National Cancer Institute (NCI) is a division of the National Institutes of Health, which is itself one of the 11 component agencies that make up the U.S. Department of Health and Human Services. Last week, the NCI quietly added to its treatment database a summary of marijuana’s medicinal benefits, including an acknowledgment that oncologists may recommend it to patients for medicinal use.

The summary cites clinical trials demonstrating the benefit of medical marijuana. Part of it reads:

The potential benefits of medicinal Cannabis for people living with cancer include antiemetic effects, appetite stimulation, pain relief, and improved sleep. In the practice of integrative oncology, the health care provider may recommend medicinal Cannabis not only for symptom management but also for its possible direct antitumor effect.

Although 34 states have passed laws recognizing marijuana’s medicinal properties and 15 states, plus Washington, D.C., have legalized it for medical use, this is the first time a federal agency has recognized it as medicine. Despite recent developments, Attorney General Eric Holder said in 2009 that the Justice Department would not raid medical marijuana facilities, but at no point did he acknowledge their legitimacy as distribution centers for medicine. A 2001 Supreme Court ruling, meanwhile, declared that medical use of marijuana cannot be considered in any federal court deliberating on a marijuana possession or distribution case.

The new NCI assessment could have an impact on the classification of marijuana as a Schedule I drug, the harshest possible drug classification, which has resulted in a prison population in which 1 in 8 prisoners in the U.S. is locked up for a marijuana-related offense. One of the principal criteria for a Schedule I determination is that there be “no currently accepted medical use in treatment in the United States.” The U.S. Justice Department may have a hard time maintaining that claim if challenged, considering a federal agency now recognizes marijuana’s medical use in cancer treatment.

From the other side of the argument comes a new white paper (PDF) from the American Society of Addiction Medicine (ASAM) censuring the prescription of marijuana by doctors in states where its medical use is legal. The ASAM takes issue with the fact that marijuana is not regulated by the U.S. Food and Drug Administration and therefore not subject to the same standards as other medicines. The white paper also cites as a health risk the fact that the most common method of using marijuana is smoking it.

Allen St. Pierre, executive director of the National Organization for the Reform of Marijuana Laws, believes that the ASAM paper is a direct response to the new NCI evaluation and that ASAM physicians have a vested interest in keeping marijuana illegal in all cases.

“These doctors are making a fortune off of marijuana prohibition,” he says. “They have a financial, proprietary interest to maintain the status quo.”

St. Pierre argues that addiction specialists would be losing a major revenue source if marijuana were legalized, decriminalized or simply recognized as medicine in federal court. Without the massive number of arrests and convictions based on marijuana-related offenses, there would be a sharp drop in the number of patients referred to a doctor for marijuana addiction counseling by judges.

“The NCI statement? Fascinating. The ASAM reply? Pathetic. And predictable,” says St. Pierre.

Dr. Andrea Barthwell, former president of ASAM, claimed in an ASAM press release that the white paper had its origins in a concern for doctor liability and responsibility.

“Allowing cannabis to circumvent FDA approval sets a dangerous precedent and puts us on a slippery slope,” she said.