Now, CBS News legal analyst and lawyer Andrew Cohen weighs in with some answers about the implications of the protection.
The guards still can be prosecuted but the immunity they've already been granted leads to a conflicting scenario where State Department officials know information about a pending criminal investigation that they are not allowed to tell federal prosecutors. And that's why the Justice Department is so hot over this.
It's unlikely that any of these employees would have willingly talked to federal prosecutors anyway about the killings. But the complaint from the Justice Department is that State Department officials had no business cutting a deal with the Blackwater guards without clearing such a deal first with Justice.
The State Department has the legal authority to grant use immunity, which gives the person testifying a free pass for his or her testimony but does not preclude a criminal case based upon independent evidence. The reason this is a controversy is because the department offered these deals without first clearing it with federal prosecutors — a shocking breach of protocol.