The U.S. Court of Appeals for the Ninth Circuit became the second appellate court Thursday to wade into reasonable and nondiscriminatory patent licensing, upholding a $15 million judgment for Microsoft against Motorola but sidestepping one of the nagging questions in the area.

A panel led by Judge Marcia Berzon affirmed a groundbreaking 2013 award—the result of a combination bench and jury trial before U.S. District Judge James Robart of Washington—that arose from Motorola Inc.’s demand for a 2.25 percent royalty on Microsoft Corp.’s Xboxes and Windows products.