ReDigi has created software that purports to remove old digital music files from the user's equipment and then allow that user to resell these files through ReDigi's on-line marketplace. Capitol Records filed suit against the company in 2012 claiming copyright infringement. The first sale doctrine seems to suggest that a purchased copy can be legally sold. But is a digital copy a true "copy" under copyright law?
UPDATE: In April 2013 the Court granted summary judgment for Capitol Records, finding that ReDigi's online sale of digital music constitutes copyright infringement. This ruling creates a distinction between physical items and digital ones. While this case applies to digital music, it may affect the resale of all digital works including e-books. ReDigi may appeal.