The person-in-charge of a conveyance shall not permit the loading at a customs station,-

(a) of export goods, other than baggage and mail bags, unless a shipping bill or bill of export or a bill of transhipment, as the case may be, duly passed by the proper officer, has been handed over to him by the exporter;

(b) of baggage and mail bags, unless their export has been duly permitted by the proper officer.