[JURIST] The US Supreme Court [official website; JURIST news archive] ruled Wednesday that plaintiffs in a patent-tying antitrust action under Section 1 [text] of the Sherman Act must prove that the defendant has market power as part of its affirmative case. In Illinois Tool Works v. Independent Ink [Duke Law case backgrounder], 04-1329, Independent Ink sued under the Sherman Act, arguing that an Illinois Tool Works company illegally tied unpatented ink to its patented printheads and ink containers. The US Court of Appeals for the Federal Circuit ruled [PDF text] that market power, the defendant's ability to raise prices for a product, could be presumed when the tying product is patented.

The Supreme Court held that "a patent does not necessarily confer market power upon the patentee" and that "in all cases involving a tying arrangement, the plaintiff must prove that the defendant has market power in the tying product." Read the Court's unanimous opinion [PDF text] per Justice Stevens. Justice Alito did not take part in the decision, which was argued before his confirmation.