What is the rule under which TSA conducts the threat assessment?

The rule is 49 CFR 1572. On May 5, 2003, TSA published the rule to secure the transportation of hazardous materials (hazmat), including explosives, by requiring threat assessments for all individuals who apply for, renew, or transfer a Hazardous Materials Endorsement (HME) on their commercial driver’s license (CDL). On January 25, 2007, TSA modified this rule to include additional disqualifiers and appeal mechanisms.