MINNEAPOLIS (WCCO) — A Star Tribune Minnesota Poll out Tuesday found that a slight majority – 51 percent — of Minnesotans favor legalizing medical marijuana. Already, 20 other states allow it, but patients must buy it through shops and dispensaries.

So, why can’t pharmacies sell medical marijuana?

“That’s a difficult question,” said Heather Azzi, director of Minnesotans for Compassionate Care, a group that’s been working to legalize medical marijuana in Minnesota for a decade. “The problem is a political one.”

In 1970, Congress passed the Controlled Substances Act, which labeled marijuana as a Schedule I substance.

The Justice Department defines Schedule I drugs as having “no currently accepted medical use and high potential for abuse.” It’s the highest classification for a controlled substance, right alongside heroin. In recent Congressional testimony Michael Botticelli, the deputy director of the Office of National Drug Control Policy, indicates that federal opinion might not change anytime soon.

“The Department of Justice’s responsibility to enforce the CSA (Controlled Substances Act) remains unchanged,” Botticelli said before the House Oversight Committee’s Government Operations subpanel on Feb. 4.

All doctors and pharmacists in the U.S. have to be licensed by the Drug Enforcement Administration.

“If a pharmacist or physician were to prescribe or to dispense marijuana, they could lose that registration with the federal government and would no longer be able to prescribe any controlled substance,” Azzi said.

In almost all cases, drugs sold in pharmacies must be FDA approved. Marijuana’s classification as a Schedule I controlled substance prevents significant research from even allowing that to happen.

In a Feb. 12 New York Times op-ed, doctors with the NYU Comprehensive Epilepsy Center wrote, “The truth is we lack evidence not only for the efficacy of marijuana, but also for its safety.”

Azzi argues medical marijuana has been used for thousands of years and has been shown to provide comfort and help to patients with a variety of conditions. She says any medical marijuana law passed in Minnesota would require strict regulation by the state’s Department of Health.

Dr. Ilo Leppik, a professor of pharmacy and neurology at the University of Minnesota, says the law makes it difficult to get research grants and makes drug companies avoid medical marijuana research. He says he wouldn’t prescribe marijuana in its whole form because it has too many chemicals that could have negative side effects, it often must be smoked and it’s difficult to control its concentration. He’d like to see more research on purifying some of the specific chemicals inside the plant to make them into pill form.

“There are a lot of things that Congress does that don’t make a lot of sense and do hamper medical care and medical research,” he said.