Updated

A federal judge on Tuesday blocked the importation of a drug used in executions on grounds the Food and Drug Administration ignored the law in allowing it into this country.

U.S. District Judge Richard Leon sided with lawyers for death row inmates in Tennessee, Arizona and California who want to keep out sodium thiopental, because it is an unapproved drug manufactured overseas. The Obama administration argued it had discretion to allow unapproved drugs into the U.S.

But Leon said the FDA's actions were "contrary to law, arbitrary, capricious, and an abuse of discretion." He said that plain language of the law says that an article that appears to be misbranded or unapproved "shall be refused admission."

Leon scolded the agency: "Put simply, this appears to be nothing more than the FDA, once again, stubbornly clinging to every last ounce of its discretionary authority!"

Sodium thiopental is an anesthetic used to put inmates to sleep before other lethal drugs are administered. The drug's U.S. manufacturer announced last year that it would no longer produce it, which forced corrections officials to delay many executions. Many of the nation's 34 death penalty states switched to an alternative drug, pentobarbital -- a point Leon stressed.

In addition to blocking the FDA from allowing the drug into the country, Leon also ordered the FDA to immediately notify any state correctional departments with foreign-manufactured thiopental that its use is prohibited by law, and that the drug must be returned to the FDA.

A lawyer for the death row challengers, Brad Berenson, said in an email that "it was especially gratifying that the court recognized that even the most despised members of our society are entitled to the protections Congress gave to all Americans in the Food Drug and Cosmetic Act."

The FDA declined to comment on the ruling or say whether it planned to appeal.

Leon, who was appointed by President George W. Bush, dismissed the FDA's contention that the death row inmates lacked standing.

"Here, the threatened injury -- that unapproved foreign thiopental will fail to anesthetize plaintiffs properly during execution, causing conscious suffocation, pain, and cardiac arrest -- is, to say the least, severe," the judge wrote. "Indeed, few in our society are more vulnerable than a death row inmate facing lethal injection."

Leon also said that the FDA was undermining its own policy of maintaining a closed drug distribution system designed to keep dangerous drugs out of U.S. commerce.

"By opening up the `closed' drug system by allowing an unapproved drug -- thiopental -- into the United States, defendants jeopardize their own system and threaten the public health by creating a risk that thiopental could incorrectly end up in the hands of the general public," he wrote.