Anthony Bolante / Reuters file A marijuana starter plant is shown at Canna Pi medical marijuana dispensary in Seattle on Nov. 20.

Advocates of looser federal restrictions on marijuana suffered a significant legal setback Tuesday, as a panel of three judges found that the federal government acted properly in refusing to loosen restrictions on pot.

Pro-marijuana groups and a disabled veteran who said it improves his medical condition asked the Drug Enforcement Administration to put marijuana on a lower tier of federal restrictions. They said the agency was ignoring a growing body of scientific evidence that it has some medical benefits. When the DEA refused, they sued.

But by a 2-1 vote, a panel of the US Court of Appeals for the District of Columbia said Tuesday that the DEA did consider all the available information. "We find nothing in the record that could move us to conclude that the agency failed to prove by substantial evidence that such studies confirming marijuana's medical efficacy do not exist," the majority opinion said.

The ruling comes as a stark contrast to actions by a growing number of states that allow use of marijuana on the recommendation of a doctor. And voters in Colorado and Washington approved ballot measures in November that ease state restrictions against recreational use.

The DEA has long classified marijuana as a Schedule I drug, the most-restrictive category, finding it "has no currently accepted medical use in treatment in the United States." The production, sale, and use of marijuana remain illegal under federal law as a result.

Judge Harry Edwards, who wrote Tuesday's opinion, took note of the controversy. "There is a serious debate in the United States over the efficacy of marijuana for medicinal uses," he said.

But the issue for the court, he said, "is not whether marijuana could have some medical benefits." Instead, Edwards said, the court's job was to determine whether the DEA acted within the scope of its authority in declining to reclassify the drug, given claims in the lawsuit that peer-reviewed scientific studies found some evidence that it could be beneficial.

"We defer to the agency's interpretation of these regulations and find that substantial evidence supports its determination" that no studies exist that are "adequate and well-controlled" proving its effectiveness in medical treatments.

The dissenting judge, Karen LeCraft Henderson, expressed no view on whether marijuana has medical benefits. Instead, she said the court should have dismissed the case on the grounds that none of those filing the lawsuit had legal authority to bring the case to court in the first place.