EMI is suing ReDigi, a company that lets consumers resell their MP3s for copyright infringement. This isn’t a huge surprise, since unlike selling a used CD, a used MP3 is theoretically the same as a new one.

The New York Times has more from the complaint: “‘While ReDigi touts its service as the equivalent of a used record store, that analogy is inapplicable: used record stores do not make copies to fill their shelves,’ the complaint says. ‘ReDigi is actually a clearinghouse for copyright infringement and a business model built on widespread, unauthorized copying of sound recordings.’”

The whole concept of selling used digital content is tough. Yes, it was nice in the days of print to resell records, CDs, DVDs and books that you have already listened to or read, and to pick up used copies of other people’s old media at a cheaper price. But how do you do this with digital content?

A couple of years ago we heard about a company called Lexink who wanted to let consumers sell “used” copies of eBooks that they had already read using a tool call Unloaded. We haven’t heard much from them about that initiative since them, likely because they couldn’t get publishers to give them permission to sell perfectly good digital copies of copyrighted content.

However, their website still includes a description of the Unloaded tool for reselling used MP3s and movies. The website explains how it works: “UNLOADER is integrated into the Media Player digital download store so once you unload a title and someone purchases it, the media vanishes from your library and you can no longer play it. You get store credit that you can redeem for other unloaded content on the resale store or brand new titles from the online store.”

From the EMI lawsuit, it sounds like this kind of business model isn’t without its issues. Is there any way to create a business model out of selling used content that could work for record labels, publishers and consumers?