So if I understand correctly the history here, Righthaven doesn't actually purchase the IP from the copyright holders. They obtain the rights to sue in the copyright holders name (and take part of the proceeds).
I believe in this case the judge found that there's no legal ability for Righthaven to be a plaintiff in a copyright case where they don't own the rights to the actual IP.
In particular, the reasoning that other court cases have adopted is that the Copyright Act only allows suits by "the legal or beneficial owner of an exclusive right under a copyright", and then goes on to list six exclusive rights: reproduction, production of derivative works, distribution, and three kinds of public-performance rights (e.g. of audio transmissions, of public film showings, etc.). So, Righthaven would need to own at least one of those six rights regarding a work to sue over it, which it doesn't.
I believe in this case the judge found that there's no legal ability for Righthaven to be a plaintiff in a copyright case where they don't own the rights to the actual IP.