Any employer and any officer, vice principal or agent of any employer who shall violate any of the provisions of RCW 49.52.050 (1) and (2) shall be liable in a civil action by the aggrieved employee or his or her assignee to judgment for twice the amount of the wages unlawfully rebated or withheld by way of exemplary damages, together with costs of suit and a reasonable sum for attorney's fees: PROVIDED, HOWEVER, That the benefits of this section shall not be available to any employee who has knowingly submitted to such violations.