49 U.S.C. § 31302

Commercial driver’s license requirement

No individual shall operate a commercial motor vehicle without a valid commercial driver’s license issued in accordance with section 31308. An individual operating a commercial motor vehicle may have only one driver’s license at any time and may have only one learner’s permit at any time.

( Pub. L. 103–272, § 1(e) , July 5, 1994 , 108 Stat. 1015 ; Pub. L. 105–178, title IV, § 4011(b)(1) , June 9, 1998 , 112 Stat. 407 ; Pub. L. 109–59, title IV, § 4122(1) , Aug. 10, 2005 , 119 Stat. 1734 .)