Trident, owned by Illinois Tool Works, sold a patented printhead used in putting bar codes on cartons, and required its customers who bought the printhead to also buy its unpatented ink. Aptly named Independent Ink wanted in on the market, so it sued under the Sherman Act, antitrust law, which forbids companies from tying a license to use one product to another product. The district court found for Trident, noting that Independent Ink had failed to show that Trident's control of the printhead allowed them to raise prices above the competitive market rate. The CAFC reversed, finding that the power of a patent came with a presumption of market power, that is, the ability to raise prices, leaving the burden on the defendant to show that such power did not exist. Here, the Supreme Court reverses the appeals court.

Held: Because a patent does not necessarily confer market power upon the patentee, in all cases involving a tying arrangement, the plaintiff must prove that the defendant has market power in the tying product.

(a) Over the years, this Court's strong disapproval of tying arrangements has substantially diminished, as the Court has moved from relying on assumptions to requiring a showing of market power in the tying product. The assumption in earlier decisions that such "arrangements serve hardly any purpose beyond the suppression of competition," Standard Oil Co. of Cal. v. United States, 337 U. S. 293, 305-306, was rejected in United States Steel Corp. v. Fortner Enterprises, Inc., 429 U. S. 610, 622 (Fortner II), and again in Jefferson Parish Hospital Dist. No. 2 v. Hyde, 466 U. S. 2, both of which involved unpatented tying products. Nothing in Jefferson Parish suggested a rebuttable presumption of market power applicable to tying arrangements involving a patent on the tying good.

(b) The presumption that a patent confers market power arose outside the antitrust context as part of the patent misuse doctrine, and migrated to antitrust law in International Salt Co. v. United States, 332 U. S. 392. See also Morton Salt Co. v. G. S. Suppiger Co., 314 U. S. 488; United States v. Loew's Inc., 371 U. S. 38. Pp. 8-10.

(c) When Congress codified the patent laws for the first time, it initiated the untwining of the patent misuse doctrine and antitrust jurisprudence. At the same time that this Court's antitrust jurisprudence continued to rely on the assumption that tying arrangements generally serve no legitimate business purpose, Congress began chipping away at that assumption in the patent misuse context from whence it came. Then, four years after Jefferson Parish repeated the presumption that patents confer market power, Congress amended the Patent Code to eliminate it in the patent misuse context. While that amendment does not expressly refer to the antitrust laws, it invites reappraisal of International Salt's per se rule. After considering the congressional judgment reflected in the amendment, this Court concludes that tying arrangements involving patented products should be evaluated under the standards of cases like Fortner II and Jefferson Parish rather than the per se rule in Morton Salt and Loew's. Any conclusion that an arrangement is unlawful must be supported by proof of power in the relevant market rather than by a mere presumption thereof. Pp. 11-13.