No employer shall knowingly allow, permit, require, or authorize a driver to drive a commercial motor vehicle under any of the following conditions:
(a) The driver has a driver’s license or privilege suspended, revoked, or canceled by any state or has been disqualified from operating a commercial motor vehicle.
(b) The driver has more than one driver’s license.
(c) The driver or the commercial motor vehicle or motor carrier operation is subject to an out-of-service order as described in subdivision (b) of Section 2800.
(d) In violation of any law or regulation pertaining to a railroad-highway grade crossing.