You can resell your vinyl records, cassette tapes, and CDs, but you can't resell your digital music files.

The "first sale" doctrine doesn't apply.

ReDigi tried hard to live up to the spirit of copyright law. It created a system where the uploader of a "purchased" iTunes song would lose access to the music after the file was transferred to the new "buyer's" computer. Yeah, right, said the record company and the judge – there's no way to ensure that the "seller" wasn't keeping the song anyway.