It appears that the deal not only rescinds immunity for mercenaries contractors, but it does so retroactively, meaning that they could be liable to stand trial in an Iraqi court for earlier actions, like shooting wildly into a crowd at a Baghdad traffic circle:

A new U.S.-Iraq security agreement doesn’t specifically prevent Iraqi officials from bringing criminal charges retroactively in cases such as the September 2007 shooting deaths of 17 Iraqi civilians by contractors protecting a State Department convoy, officials told security company officials during meetings in Washington Thursday

Good.

Hopefully this should get the mercenaries contractors out of Iraq, which would be good for both the Iraqis and our troops, who will find the Iraqi people a little bit less pissed off at Americans.