In this batch of writ petitions, the question raised relates to the liability to pay on the 'natural rubber' imported for the petitioners, additional duty under Section 3 of the Customs Tariff Act 51 of 1975, hereinafter referred to as the Act. Item-wise 'natural rubber' bears different names and in the present batch of writ petitions, we are concerned with the natural rubber bearing the name 'smoked sheets'. In some cases, the petitioners have paid the additional duty through the State Trading Corporation, which was the agency for the import of this product, since the said product was a canalised one. The State Trading Corporation, when it collected the price from the petitioners, the additional duty was part and parcel of the price paid by the petitioners. In those cases, the petitioners have asked for refund. The petitioners also apprehending levy and collection of additional duty have asked forwrits of mandamusto forbear the respondents from so levying and collecting the additional duty in respect of imports for which such payments were not yet made. In some of writ petitions, the petitioners have prayed for the issue of declaration that the levy of duty on 'natural