39 CFR 310.5 - Payment of postage on violation.
(a) Upon discovery of activity made unlawful by the Private Express Statutes, the Postal Service may require any person or persons who engage in, cause, or assist such activity to pay an amount or amounts not exceeding the total postage to which it would have been entitled had it carried the letters between their origin and destination.
(b) The amount equal to postage will be due and payable not later than 15 days after receipt of formal demand from the Inspection Service or the Manager, Mailing Standards, USPS Headquarters, unless an appeal is taken to the Judicial Officer Department in accordance with rules of procedure set out in part 959 of this chapter.
(c) Refusal to pay an unappealed demand or a demand that becomes final after appeal will subject the violator to civil suit by the Postal Service to collect the amount equal to postage.
(d) The payment of amounts equal to postage on violation shall in no way limit other actions to enforce the Private Express Statutes by civil or criminal proceedings.