Carl - I haven't the foggiest on the Iraqi Civil Code.

Blackwater and its employees were immune from prosecution under Iraqi criminal law because of an immunity agreement (from NYT article in other thread):

The guards could not be prosecuted under Iraqi law because of an immunity agreement that had been signed by the Coalition Provisional Authority, the governing authority installed by the United States after the invasion of Iraq.
Because of the way DoS Security and the DoJ-FBI handled the case, the Blackwater employees cannot be prosecuted under US criminal law - except for the guy who pleaded guilty and was flipped.

Of course, immunity from criminal prosecution does not mean immunity from civil actions for wrongful death (which could be based on as simple a theory as negligence). Again, from the NYT article:

In the Nisour Square shooting case, prosecutors did not charge Blackwater itself, but the families of several of the Iraqis who were killed have filed a civil lawsuit against the company, which has changed its name to Xe Services.
and from the AP article (also linked in the other thread):

Dozens of Iraqis, including the estates of some of the victims allegedly killed by Blackwater employees, filed a separate lawsuit last year alleging that Blackwater employees engaged in indiscriminate killings and beatings. The civil case is still before a Virginia court.
That case against Blackwater (as the target defendant) is discussed in the other thread - and appears to hinge on Iraqi civil law (see this post).

I have to admit dumbness; I'm not an SME on your questions.

Cheers

Mike