The Illinois Community Currency Exchanges Act provides for the licensing, inspection, bonding and regulation of "currency exchanges" engaged in the business of issuing or selling money orders. It forbids them to do business on the premises of any other business; but it exempts from all of its provisions money orders sold or issued by the American Express Co., an old, established, world-wide enterprise of unquestioned solvency and high financial standing, which sells money orders through local drug and grocery stores. Appellees, a "currency exchange" issuing and selling money orders and its agent selling them in his own drugstore, sued to enjoin enforcement of the Act against them, on the ground of its unconstitutionality. Held: Application of the Act to appellees denies them the equal protection of the laws guaranteed by the Fourteenth Amendment. Pp. 458-470.

(a) The Equal Protection Clause does not require that every state regulatory statute apply to all in the same business; but a statutory discrimination must be based on differences that are reasonably relate