Permits to operate on the highways a vehicle exceeding the maximum weight specified in this title shall be granted for a vehicle hauling containerized cargo in a sealed, seagoing container bound to or from a seaport and has been or will be transported by marine shipment and for a tank vehicle hauling fluid milk. In order for a vehicle hauling containerized cargo in a sealed, seagoing container bound to or from a seaport to qualify for such a permit, the contents of such seagoing container shall not be changed from the time it is loaded by the consignor or his agents to the time it is delivered to the consignee or his agents. Cargo moving in vehicles conforming to specifications shown in this section shall be considered irreducible and eligible for permits under regulations of the Commissioner. The fee for a permit issued under this section shall be as provided in § 46.2-1140.1. Only the Commissioner may issue a permit under this section. For purposes of this section “tank vehicle” has the same meaning ascribed to it in § 46.2-341.4.