Champerty is a doctrine of law which forbids certain situations in which a third party pays litigation expenses in return for a share in any proceeds. 

It’s an interesting idea for a defence to a patent ‘troll’ suit.  Peter Zura and Mark Walters have each commented on it in the past. 

Of course, it would only work against those ‘trolls’ who don’t own or licence the asserted patents.  Still, it will be interesting to see if it goes anywhere.