"Now if the cnn "armed guard" did kill someone at the checkpoint is it manslaughter? CNN willingly and knowingly instigated the situation..... "

Interesting question. It may not be enforceable, and therefore irrelevant.
If you consider that the Iraq regime (under Saddam) exists, then I would guess that the body guard could be consider an unlawful combatant, and if an unlawful combatant if he kills a soldier then that would be murder.
One problem with this would be that it wasn't clear that person at the check point was a uniformed soldier. If the people at the check point were not legal soldiers, then it's quite simple- they did not have the right to stop the car and they shot first, thereby allowing the convoy to defend themselves. It's also possible that since the Iraq regime has repetitively violated the rules of war it's also reasonable that even if the person at the check point was a uniformed soldier, reporters couldn't be sure that these soldiers were actually soldiers or that they would follow the rules of warfare.
Another problem was that I believe the reporters were ordered to see some governor or something. I believe if a soldier orders a citizen to do something then that citizen would be required to follow that order. The question would be was that actually a soldier and did that soldier order or merely say that if they wanted to be there they had to do first see the governor. If a soldier is giving an order, then soldiers or non combatants might be able to legally enforce that order.
Finally it seemed to me that the intent of the reporter was to go into the city in which was not controlled by the Saddam regime- but instead had thought the city had fallen within the last couple of hours. Intent is a consideration as far as being an unlawful combatant. Also it's interesting as far as international law and how that relates responsiblity of CNN in regards to the action of one of their bodyguards.