After the Court of Justice of the European Union ruled that software downloads can be resold, GameStop has started looking into options for reselling downloadable games. While it's not clear if GameStop is doing this because of the ruling, it is likely the cause of their exploration into options regarding the matter.
GameStop would like to add this to its business as reselling used games is a big portion of its revenue. In 2011, GameStop managed $2.6 billion in used game sales alone, a number which has steadily increased since 2002's $300 million. Curiously enough, used game sales still make up roughly the same percentage of revenue. In 2002 that number was 22% and in 2011 the number rose to only 27%.
Game developers and publishers don't like the used game market as it cuts into their sales. As they receive no cut from any of the sales, each used game sale is roughly a lost sale to them. Not every used game sale would have been a new sale, however. They'd be happy if used game sales would completely cease to exist.