Lastly, it was argued on behalf of the appellant that the notification dated January 16, 1951 revoking the tax concessions was in violation of article 306 of the Constitution which provides as follows: "Notwithstanding anything in the foregoing provisions of this Part or in any other provisions of this Constitution, any State specified in Part B of the First Schedule which before the commencement of this Consti tution was levying any tax or duty on the import of goods into the State from other States or on the export of goods (1) [1963] Supp. 2 S.C.R. 515. 91 from the State to other States may, if an agreement in that behalf has been entered into between the Government of India and the Government of that State, continue to levy and collect such tax or duty subject to the terms of such agreement and for such period not exceeding ten years from the commencement of this Constitution as may be specified in the agreement.