A Utah federal judge struck down Thursday the U.S. government's year-old ban on dietary supplements containing ephedra, a once wildly popular weight-loss and body-building aid pulled from the market after it was linked to at least a hundred deaths.

Ruling in favor of a Park City-based company that has sold ephedrine-alkaloid supplements for two decades, U.S. District Judge Tena Campbell determined the Food and Drug Administration had failed to shoulder its burden of proof that the amphetamine-like herb is unsafe in low doses.

"Simply stated, to declare all (ephedrine supplements) adulterated, as it has done, the FDA must prove that any dose, no matter how small, presents a significant or unreasonable risk of illness of injury," Campbell wrote.

The ruling does not declare ephedrine, a stimulant that speeds the heart rate and constricts blood vessels, safe. Rather, it takes issue with the FDA's administrative procedures in passing the ban.

Under the Dietary Supplement Health and Education Act of 1994, dietary supplements are regulated as a food, rather than a drug, and are presumed safe unless the government presents evidence to the contrary.

And that is what the agency failed to do prior to passing its February 2004 rule banning the sale of stimulants containing any amount of ephedrine, the judge said. In an administrative record of more than 130,000 pages, there is only one specific reference to the effects of low-dose ephedrine, the ruling states.

"The FDA's imposition of a risk-benefit analysis places a burden on the producers of (ephedrine supplements) to demonstrate a benefit as a precondition to sale, and that is contrary to Congress' intent," Campbell wrote.

Nutraceutical Corp. and its subsidiary, Solaray Inc., sued the FDA in May 2004, one month after the ephedra ban went into effect. Attorney Jonathan Emord on Thursday hailed the ruling as a declaration that the agency failed in its charge to prove that all levels of ephedra are harmful, even the 10 milligrams per dose found in his clients' products.

"This judge is doing an extraordinary service for the American public because she is ensuring that this government does not abuse its discretion and take off the market anything it dislikes without scientific proof," he said. "This is a case where the FDA used the context of ephedra and the political environment that surrounded it as a basis for greatly expanding its authority to take a dietary supplement off the market."

FDA spokeswoman Kimberly Rawlings said the agency is still evaluating Campbell's ruling and declined further comment.

Thursday's ruling sends the matter back to the FDA, which must now take another look at its evidence in banning all forms of ephedrine. It also forbids the FDA from taking enforcement action against Nutraceutical for any future sales of dietary supplements containing 10 milligrams or less of ephedrine alkaloids per dose.