ABC News has the text of the Blackwater immunity deal:

I understand this statement is being given in furtherance of an official administrative inquiry,” and that, “I further understand that neither my statements nor any information or evidence gained by reason of my statements can be used against me in a criminal proceeding, except that if I knowingly and willfully provide false statements or information, I may be criminally prosecuted for that action under 18 United States Code, Section 1001.

While the State Department claims that this still allows for prosecution, the case clearly indicates otherwise, particularly in the DC Circuit Court, where this would almost certainly be heard.

Josh Marshall called on “a highly knowledgeable source“, and their assessment was that “Use Immunity”, pretty much eliminates the possibility of presecution:

• Prosecutors, “would then have to prove that every piece of evidence used in the prosecution was obtained completely independent of the employees’ statements.” (emphasis mine)
• The DC circuit has an even more extreme view, where the prosecution, “would also have to show that none of their witnesses had heard what the employees said in their immunized statements.”prosecution was obtained completely independent of the employees’ statements.” (emphasis mine)

Additionally, even if there was no authorization and the immunity was granted in error, the courts, particularly the DC Circuit, generally still treat it as if it were.

I call coverup.