(3) Any law of a State shall, in so far as it imposes, or authorises the imposition of,
(a) a tax on the sale or purchase of goods declared by Parliament by law to be of special importance in inter State trade or commerce; or
(b) a tax on the sale or purchase of goods, being a tax of the nature referred to in sub clause (b), sub clause (c) or sub clause (d) of clause 29 A of Article 366, be subject to such restrictions and conditions in regard to the system of levy, rates and other incidents of the tax as Parliament may by law specify