Padilla, a U.S. citizen arrested in 2002 and declared an "enemy combatant," had sought to sue John Yoo, a deputy assistant attorney general in President George W. Bush's Department of Justice, over "gross physical and psychological abuse" Padilla said he endured while in military detention more than three years, the Los Angeles Times reported.
Padilla said he endured death threats and was given psychotropic drugs, shackled and manacled for extended periods, denied contact with family members or a lawyer for 21 months and not treated for medical conditions that could have been life-threatening.
"That such treatment was torture was not clearly established in 2001-03," Judge Raymond C. Fisher, a Bill Clinton appointee, wrote for the 9th Circuit Court of Appeals.
Yoo, now a law professor at the University of California, Berkeley, advised the government on techniques the military could use to detain and interrogate terrorism suspects.
The appeals court noted the Supreme Court didn't declare U.S. citizens held as enemy combatants have constitutional rights until 2004.
Today, the 9th Circuit Court said, "it remains murky whether an enemy combatant detainee may be subjected to conditions of confinement and methods of interrogation that would be unconstitutional if applied in the ordinary prison and criminal settings."
U.S. officials said Padilla was detained after the discovery of his involvement in a plot to attack the United States with a radioactive "dirty bomb." After his military detention, he was transferred to civilian custody and was later convicted of conspiracy to commit terrorism.
The Times said the conviction was based on evidence unrelated to allegations under which Padilla was held in military detention.