Suddenly, on that May day in 2005, the copter dropped CS gas, a riot-control substance the American military in Iraq can use only under the strictest conditions and with the approval of top military commanders. An armored vehicle on the ground also released the gas, temporarily blinding drivers, passers-by and at least 10 American soldiers operating the checkpoint.
Both the helicopter and the vehicle involved in the incident at the Assassins’ Gate checkpoint were not from the United States military, but were part of a convoy operated by Blackwater Worldwide, the private security contractor that is under scrutiny for its role in a series of violent episodes in Iraq, including a September shooting in downtown Baghdad that left 17 Iraqis dead.
Officers and noncommissioned officers from the Third Infantry Division who were involved in the episode said there were no signs of violence at the checkpoint. Instead, they said, the Blackwater convoy appeared to be stuck in traffic and may have been trying to use the riot-control agent as a way to clear a path.
The military, however, tightly controls use of riot control agents in war zones. They are banned by an international convention on chemical weapons endorsed by the United States,although a 1975 presidential order allows their use by the United States military in war zones under limited defensive circumstances and only with the approval of the president or a senior officer designated by the president.
“It is not allowed as a method or means of warfare,” said Michael Schmitt, professor of international law at the Naval War College in Newport, R.I. “There are very, very strict restrictions on the use of CS gas in a war zone.”
Also see, Blackwater Mercenaries Poised to Get Fat New Pentagon Contract for "Drug War"
Probably has something to do with THIS GUY .
Laura Carlsen over at FPIF gives a pretty good rundown HERE.