Article 286 of Indian Constitution

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

(1) No law of a State shall impose, or authorize the imposition of, a tax on [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 [goods or services or both]into, or export of the [goods or services or both]out of, the territory of India.

[(2) Parliament may by law formulate principles for determining when a [supply of goods or of services or both]in any of the ways mentioned in clause (1).]