The main impediments to trying Nkunda have to do with issues over extradition to the Democratic Republic of the Congo, including the fear that the DRC's amnesty law will allow Nkunda to walk free and the fact that Rwandan law prohibits extradition to states that use the death penalty, which the DRC does. Of course, the real place Nkunda should be tried is the ICC, and don't think for a minute that it wouldn't be possible for Rwanda to arrange a transfer of Nkunda directly into MONUSCO's hands, where he could be transferred to ICC custody with little fuss, thus avoiding the Congolese courts entirely. But that would mean a full trial of Nkunda in the public eye, which no one in Rwanda wants, because, as we've discussed before, Nkunda knows everybody's secrets and would have little to lose by exposing them.
Meanwhile, back in Goma, Nkunda's one-time-number-two/current leader of the CNDP/possible leader in the FARDC (depending on whom you ask) Bosco Ntaganda has been involved in some shenanigans of his own of late, most recently involving a Nigerian plane that arrived in Goma carrying several million dollars in cold hard cash, apparently to buy gold. From Ntaganda. You can't make this stuff up, although, as Jason notes, one has to wonder about the type of shady characters who think Goma is the place to buy gold. Everybody knows the gold goes through Butembo, Bunia, and Bukavu. Duh.