[…] WASHINGTON — The helicopter was hovering over a Baghdad checkpoint into the Green Zone, one typically crowded with cars, Iraqi civilians and United States military personnel.
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.
“This was decidedly uncool and very, very dangerous,” Capt. Kincy Clark of the Army, the senior officer at the scene, wrote later that day. “It’s not a good thing to cause soldiers who are standing guard against car bombs, snipers and suicide bombers to cover their faces, choke, cough and otherwise degrade our awareness.” […]
Use of CS Gas in war is prohibited under the terms of the 1997 Chemical Weapons Convention (signed in 1993) because it could trigger retaliation with more toxic agents such as nerve gas. Domestic police use of CS, however, is legal in many countries.
So we now do the very thing that we went after Saddam for? Once again from the same Wikipedia article (here):
Iraq successfully developed CS during the 1970s and during the 1980s produced tons of the substance firstly at Salman Pak and later at al-Muthanna. Saddam Hussein used CS against the Kurds in his own country and against Iran during the Iran-Iraq War.
Admittedly, we do use the same gas against our own people on occasion. (Waco Seige, for example.)