Copyright misuse. After Psystar's antitrust and monopoly arguments were thrown out, it tried to argue that Apple was misusing its copyright on OS X by limiting it to Apple hardware. It was an interesting and ballsy argument, and the court didn't buy it for a second: "Apple has not prohibited others from independently developing and using their own operating systems. Thus, Apple did not violate the public policy underlying copyright law or engage in copyright misuse." Put another way, as long as Apple doesn't try to prevent OS X owners from buying Windows PCs, it can sell OS X however it wants.