Armed with a new study that showed smoking marijuana eased pain in some HIV patients, medical marijuana advocates sued the federal government Wednesday over its claim that pot has no accepted medical benefits.

The lawsuit filed in U.S. District Court by Americans for Safe Access accuses the U.S. Department of Health and Human Services of engaging in "arbitrary and unlawful behavior" that prevents "sick and dying persons from seeking to obtain medicine that could provide them needed, and often lifesaving relief."

The Oakland-based advocacy group wants a judge to force the department and the Food and Drug Administration to stop giving out information that casts doubt on the efficacy of marijuana in treating various illnesses.

"The FDA position on medical cannabis is incorrect, dishonest and a flagrant violation of laws requiring the government to base policy on sound science," Joe Elford, chief counsel for Americans for Safe Access, said in a statement.

California is one of 11 states where marijuana use is legal for people with a doctor's recommendation, but because the U.S. government does not recognize pot's medical benefits patients can still be arrested and prosecuted by federal authorities.

Last week, researchers from the University of California, San Francisco reported in the journal Neurology that a test involving 50 HIV patients showed that those who smoked pot experienced much less pain than those given placebos.

Americans for Safe Access said in the lawsuit that Health and Human Services has rejected its requests to retract the assertion that cannabis "has no currently accepted medical use in treatment in the United States," a position the agency has advertised since 2000.

Countering that statement by petitioning the government and distributing evidence that marijuana eases the symptoms of cancer, multiple sclerosis, HIV and other conditions has cost Americans for Safe Access more than $100,000, the group said in its suit.

The Department of Health and Human Services did not immediately have a response to the lawsuit.