Ala. Code § 40-25-22: Effect of Federal Legislation.

Should the collection of any taxes under this article be prevented by the operation of the provisions of the Constitution of the United States relating to interstate or foreign commerce, the Legislature hereby declares that should the Congress of the United States pass any legislation authorizing the taxation by the states of interstate or foreign commerce, sales, shipments or receipts, or commodities transported therein, or receipts of sales therein, then the provisions of this article shall apply to such sales, shipments or receipts as fully and completely as provided herein as to intrastate sales, shipments and receipts, to the extent that such act or acts of Congress authorizes and permits.