49 U.S.C. § 30124Section
§ 30124. Nonuse of safety belts
A motor vehicle safety standard prescribed under this chapter may not require a manufacturer to comply with the standard by using a safety belt interlock designed to prevent starting or operating a motor vehicle if an occupant is not using a safety belt.
(Pub. L. 103–272, §1(e), July 5, 1994, 108 Stat. 957; Pub. L. 112–141, div. C, title I, §31202(a)(2), July 6, 2012, 126 Stat. 757.)