Contraband oil shipped or transported in interstate commerce in violation of the provisions of this chapter shall be liable to be proceeded against in any district court of the United States within the jurisdiction of which the same may be found, and seized for forfeiture to the United States by a process of libel for condemnation; but in any such case the court may in its discretion, and under such terms and conditions as it shall prescribe, order the return of such contraband oil to the owner thereof where undue hardship would result from such forfeiture. The proceedings in such cases shall conform as nearly as may be to proceedings in rem in admiralty, except that either party may demand a trial by jury of any issue of fact joined in any such case, and all such proceedings shall be at the suit of and in the name of the United States. Contraband oil forfeited to the United States as provided in this section shall be used or disposed of pursuant to such rules and regulations as the President shall prescribe.
No such forfeiture shall be made in the case of contraband oil owned by any person (other than a person shipping such contraband oil in violation of the provisions of this chapter) who has with respect to such contraband oil a certificate of clearance which on its face appears to be valid and to have been issued by a board created under authority of section 715d of this title, certifying that the shipment in question is not contraband oil, and such person had no reasonable ground for believing such certificate to be invalid or to have been issued as a result of fraud or misrepresentation of fact.