No employer may knowingly allow, require, permit, or authorize a driver to operate a CMV in the United States:

(a) During any period in which the driver has a CMV driver’s license suspended, revoked, or canceled by a State, has lost the right to operate a CMV in a State, or has been disqualified from operating a CMV;

(b) During any period in which the driver has more than one CMV driver’s license;

(c) During any period in which the driver, or the CMV he or she is driving, or the motor carrier operation, is subject to an out-of-service order; or

(d) In violation of a Federal, State, or local law or regulation, pertaining to railroad-highway grade crossings.

[52 FR 20587, June 1, 1987; 52 FR 32926, Sept. 1, 1987, as amended at 59 FR 26028, May 18, 1994; 64 FR 48110, September 2, 1999]