Finance, Property, Contracts
(1) A state law cannot tax a supply of goods/services occurring outside the state, or in the course of import into or export out of India. (2) Parliament may formulate principles determining when a supply falls into these categories.
This prevents states from taxing transactions that genuinely fall outside their own territory or that are part of international trade - keeping state sales/supply taxation confined to transactions genuinely connected to that state, and keeping international trade taxation as a Union matter.
A state cannot impose its own tax on goods being exported out of India through that state's port, since export transactions are constitutionally placed beyond individual states' taxing power under this article.