The article mentions that he can't resell them, which begs the questions: Why and how? What is stopping me and the author from publishing a book _we_ wrote on

The article mentions that he can't resell them, which begs the questions: Why and how? What is stopping me and the author from publishing a book _we_ wrote on an ISBN _he_ bought? I'm guessing nothing. Assuming that, where do we draw the line between co-author, editor, publisher and "guy who resold an ISBN"?