I don't know anything about these entities, but it seems to me that paying for this sort of "insurance" is a waste of money. If your shooting is "justifiable," you have little to fear in the way of criminal ramifications. If your shooting turned out to be truly illegal, I can't believe anyone would agree to pay your legal fees. In short, read whatever "policy" you buy. I bet it's full of exclusions with respect to criminal acts.
I think people would be better off thinking about how they will deal with a civil suit that often follows even justifiable shootings. Facing the specter of a lawsuit, an insurer that is fighting to deny coverage for your intentional act, and the loss of a lifetime of savings and hard work ought to give anyone who owns a gun for self-defense pause.