Notwithstanding any judgment, decree or order of any court, tribunal or other authority,--
         (a) all duties of excise levied, assessed or collected or purported to have been levied, assessed or collected under the principal Act before the commencement of this Act shall, for all purposes, be deemed to be, and to have always been, as validly and effectively levied, assessed or collected as if the provisions of sections 3 and 4 of the principal Act as amended by sections 3 and 4 of this Act had been in force at all material times;
         (b) no suit or proceeding shall be maintained or continued in any court for the refund of, and no enforcement shall be made by any court of any decree or order directing the refund of, any such duty of excise which had been collected and which would have been validly collected if the provisions of sections 3 and 4 of the principal Act, as amended by sections 3 and 4 of this Act, had been in force at all material times;
         (c) refunds shall be made of all such duties of excise which have been collected but which would not have been so collected if the provisions of sections 3 and 4 of the principal Act, as amended by sections 3 and 4 of this Act, had been in force at all material times;
         (d) recoveries shall be made of all such duties of excise which have not been collected or, as the case may be, which have been refunded but which would have been collected or, as the case may be, would not have been refunded if the provisions of sections 3 and 4 of the principal Act, as amended by sections 3 and 4 of this Act, had been in force at all material times.
     Explanation. --For the removal of doubts, it is hereby declared that no act or omission on the part of any person, before the commencement of this Act, shall be punishable as an offence which would not have been so punishable if this Act had not come into force.