In a report issued by a U.S. government-funded research group tasked with studying drug abuse and addiction, researchers are admitting that marijuana is useful in killing off specific types of brain tumors.

The report — coming from a government-backed group with annual budget of over $1 billion — arrives at an awkward time for the administration following an announcement by the Department of Justice this week that it will continue to prosecute medical marjiuana cases against individuals in defiance of Congress.

According to the Daily Caller, the National Institute on Drug Abuse (NIDA) issued a revised report for the month of April, stating, “recent animal studies have shown that marijuana can kill certain cancer cells and reduce the size of others. Evidence from one animal study suggests that extracts from whole-plant marijuana can shrink one of the most serious types of brain tumors. Research in mice showed that these extracts, when used with radiation, increased the cancer-killing effects of the radiation.”

The NIDA report reflects research reported in November last year in the Molecular Cancer Therapies journal.

While one government agency is admitting the benefits of marijuana in medical treatments, the Justice Department is pushing forward with prosecuting medical marijuana users.

In December, Congress added an amendment to a spending bill ordering the Justice Department to not inhibit states where medical marijuana is legal from implementing their laws.

In a statement on Wednesday, spokesman Patrick Rodenbush said the Justice Department does not believe the amendment applies to cases against individuals or organizations.

Justice Department officials believe the amendment only stops the department from “impeding the ability of states to carry out their medical marijuana laws,” and can still go after users.

Writing at the Huffington Post, Drug Policy Alliance Director of National Affairs, Bill Piper, chastised the Justice Department, saying they are defying the will of the voters.

“Currently, 23 states and the District of Columbia have laws that legalize and regulate marijuana for medicinal purposes. And 12 states have laws on the books regulating cannabidiol (CBD) oils, a non-psychotropic component of medical marijuana which some parents are utilizing to treat their children’s seizures, ” he wrote, adding “Four states and the District of Columbia have legalized marijuana for non-medical use.”

“The Justice Department is ignoring the will of the voters, defying Congress, and breaking the law. President Obama and Attorney General Eric Holder need to rein in this out-of-control agency,” he said, calling on Congress to change federal drugs law allowing states to be free to set their own marijuana policies without federal interference.