49 CFR § 386.30 - Enforcement proceedings under part 395.
(a) General. A motor carrier is liable for any act or failure to act by an employee, as defined in § 390.5 of this subchapter, that violates any provision of part 395 of this subchapter if the act or failure to act is within the course of the motor carrier's operations. The fact that an employee may be liable for a violation in a proceeding under this subchapter, based on the employee's act or failure to act, does not affect the liability of the motor carrier.
(b) Burden of proof. Notwithstanding any other provision of this subchapter, the burden is on a motor carrier to prove that the employee was acting outside the scope of the motor carrier's operations when committing an act or failing to act in a manner that violates any provision of part 395 of this subchapter.
(c) Imputed knowledge of documents. A motor carrier shall be deemed to have knowledge of any document in its possession and any document that is available to the motor carrier and that the motor carrier could use in ensuring compliance with part 395 of this subchapter. “Knowledge of any document” means knowledge of the fact that a document exists and the contents of the document.