(1) WE have heard Sri Raja Ram Agarwal learned senior counsel for the appellants and Sri R.S. Rana for the respondents. Special .leave granted.

(2) THE appeal is against the order dated 3/09/1990 of the Allahabad High court in Civil Misc. Writ Petition No. 1072 of 1988 in which the appellants sought to assail the vires of S. 4-A(3) of the U.P. Sales Tax Act, 1948. That provision came to be introduced by U.P. Act 25 of 1985 and was further amended by U.P. Act 17 of 1987.

(3) THE High court dismissed the writ petition on the view that the contention as to the constitutional validity of the impugned provision could be raised and adjudicated in certain revision proceedings arising out of certain orders made in exercise of powers of the impugned provision which is pending before it. Learned counsel for the appellants contends that the question of the validity of a provision cannot be assailed before and pronounced upon by the authorities constituted under the Act and, as a necessary corollary, even by the High court in appeal or revision arising out of the proceedings taken by or before the authorities constituted under the Act and that question of constitutionalit