No employer shall knowingly allow, permit, require, or authorize a driver to drive a commercial motor vehicle under any of the following conditions:

1. (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.
2. (b) The driver has more than one driver’s license.
3. (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.
4. (d) In violation of any law or regulation pertaining to a railroad-highway grade crossing.