Brasscheck did some of the original detailed reporting on the use of tear gas and other chemical weapons against demonstrators way back in 1999 in connection with the WTO protests in Seattle.
The French started using it first after WW I.
At first the Brits thought it was too savage.
Then they saw the US use it against labor protestors and veterans in the 1920s and 30s and decided it was a good thing.
Now it's used regularly - and mindlessly - over the world to disrupt lawful demonstrations including in the good old USA.
Our 1999 reporting on the use of tear gas and nerve gas used on demonstrators at the Seattle WTO demonstration.