I'm a non-lawyer, and I'm curious about the Blackwater grand jury and prosecutor's thinking in this case, reported by the Washington Post:

As I understand it the Blackwater killers have been immunized from prosecution under Iraqi law. (And even if they weren't, a US Attorney and federal grand jury would lack jurisdiction to enforce an Iraqi law, would they not?)

So what's your theory as to what body of criminal law--what jurisdictional grounds--could be in the back of the prosecutors' mind in pursuing the Blackwater grand jury investigation?