Restrictions as to imposition of tax on the sale or purchase of goods

a State shall impose, or authorise the imposition of, a tax on 1[the supply of goods or of services or both, where such supply takes place]— (a) outside the State; or (b) in the course of the import of the 2[goods or services or both] into, or export of the 2 [goods or services or both]out of, the territory of India. 3 [* * * *] 4 [(2) Parliament may by law formulate principles for determining when a 5[supply of goods or of services or both] in any of the ways mentioned in clause (1).] 6 [(3) * * * *]