FAA Federal Aviation Regulations (FARS, 14 CFR)

(a) If the Administrator so requires by an amendment to an aircraft operator's security program, each aircraft operator required to conduct screening under a security program shall use an explosives detection system approved by the Administrator to screen checked baggage on international flights.

(b) No aircraft operator may use an explosives detection system that uses X-ray technology to inspect checked baggage unless a sign is posted in a conspicuous place where checked baggage is accepted, which notifies individuals that such items are being inspected by an explosives detection system and advises them to remove all X-ray, scientific, and high-speed film from checked baggage before inspection. This sign shall also advise individuals that they may request that an inspection be made of their photographic equipment and film packages without exposure to an explosives detection system. If the explosives detection system exposes any checked baggage to more than one milliroentgen during the inspection the aircraft operator shall post a sign which advises individuals to remove film of all kinds from their articles before inspection. If requested by individuals, their photographic equipment and film packages shall be inspected without exposure to an explosives detection system.