Judgment

R.C. Lahoti, J.—The High Court of Andhra Pradesh at Hyderabad has, by its impugned judgment dated April 11, 1990, allowed the writ petition filed by the respondent National Thermal Power Corporation Ltd. (hereinafter NTPCL , for short) and declared that the levy of duty by the State of Andhra Pradesh on the sales of electrical energy generated by the Corporation-respondent No.1 at its thermal power station set up at Rama­gundam, within the State of Andhra Pradesh, and sold to the Electricity Boards of Karnataka, Kerala, Tamil Nadu and the State of Goa in pursuance of contracts of sales occasioning inter-State movement of electricity is incompetent and outside the power of State Legislature. Consequently, the tax levied and collected has also been held to be without authority of law, hence liable to be refunded in accordance with law. On a prayer made by the learned Advocate General on behalf of the State of Andhra Pradesh, the High Court certified that the case involves a substantial question of law as to the interpretation of Constitution under Article 132. The appeal has been filed pursuant to the certificate so granted by the High Court. On 4.10.1991, a bench of two le