Former Deputy Assistant Attorney General John Yoo is protected from such lawsuits because the law defining torture and the treatment of enemy combatants was unsettled in the two years after the Sept. 11 terror attacks, when the memos were written, the 9th U.S. Circuit Court of Appeals said.
The memos have been embroiled in national security politics for years after laying out a broad interpretation of executive power.
A Yoo memo from 2001 advised that the military could use "any means necessary" to hold terror suspects. A 2002 memo to then-White House Counsel Alberto Gonzales advised that treatment of suspected terrorists was torture only if it caused pain levels equivalent to "organ failure, impairment of bodily function or even death."
Yoo also advised that the president might have the constitutional power to allow torturing enemy combatants.