South Dakota: S.D. Codified Laws § 10-45-9.
S.D. Codified Laws § 10-45-9. Constitutional and statutory exemptions from taxation
There are hereby specifically exempted from the provisions of this chapter [Retail Sales Tax] and from the computation of the amount of tax imposed by it, the gross receipts from sales of tangible personal property and any product transferred electronically which this state is prohibited from taxing under the Constitution or laws of the United States or under the Constitution or laws of the State of South Dakota.