OK, serious question here: while the law is building the case to support a child abuse indictment, the child dies from said abuse.
At that point, the only thing we can do is exact societal retribution against the perpetrator, because it's too late to help the kid.
How do you propose to resolve this conundrum? I don't think you can merely tell minor children, "Sorry, kiddies, but if you have the misfortune to have a nutball for a parent, you're hosed." The goal here is to protect children. And my experience with CPS cases is that the parent always thinks he or she is a good parent--even when the "chastisement" applied consisted of liberally applying a Louisville Slugger to the kid.
ELF is planning destruction on civilation. They haven't been arrested. They haven't broken the law yet. Until they do, and many may die when they do, the FBI has no case.
Equal protection under the law