“….Section 518 prohibits the pricing regime petitioners wish to employ. Section 518 does not define “surcharge.” Relying on the term’s ordinary meaning, the Court of Appeals concluded that a merchant imposes a surcharge when he posts a single sticker price and charges a credit card user more than that sticker price. This Court “generally accord[s] great deference to the interpretation and application of state law by the courts of appeals.” Pembaur v. Cincinnati, 475 U. S. 469, 484, n. 13. Because the interpretation of the Court of Appeals is not “clearly wrong,” Brockett v. Spokane Arcades, Inc., 472 U. S. 491, 500, n. 9, this Court follows that interpretation. Pp. 6–8.
Section 518 regulates speech. The Court of Appeals concluded that §518 posed no First Amendment problem because price controls regulate conduct, not speech. Section 518, however, is not like a typical price regulation, which simply regulates the amount a store can collect. The law tells merchants nothing about the amount they are allowed to collect from a cash or credit card payer. Instead, it regulates how sellers may communicate their prices. In regulating the communication of prices rather than prices themselves, §518 regulates speech. Because the Court of Appeals concluded otherwise, it did not determine whether §518 survives First Amendment scrutiny. On remand the Court of Appeals should analyze §518 as a speech regulation….”