Spirit founding bassist Mark Andes and the trust that handles California's royalties are working with Philadelphia lawyer Francis Alexander Malofiy, who says he is going to file a copyright infringement lawsuit and seek an injunction to block the rerelease of "Led Zeppelin IV" (as part of that band's expanded reissue series, which starts next month), according to Business Week.

They report that California's estate - and the group's members - believe the acoustic introduction to "Stairway" was lifted from their 1968 instrumental, "Taurus."