Federal agents who detained a college student after an airport screener found him carrying Arabic-English flashcards with such words as "bomb" and "terrorist" cannot be sued for their actions, a U.S. appeals court said Tuesday.

"It is simply not reasonable to require TSA officials to turn a blind eye to someone trying to board an airplane carrying Arabic-English flashcards with words such as 'bomb,' 'to kill,' etc," he said. "Basic common sense would allow those officials to take reasonable and minimally intrusive steps to inquire into the potential passenger's motivations."