Use of CS in war is prohibited under the terms of the 1997 Chemical Weapons Convention, signed by most nations in 1993 with all but five other nations signing between the years of 1994 through 1997. The reasoning behind the prohibition is pragmatic: use of CS by one combatant could easily trigger retaliation with much more toxic chemical weapons such as nerve agents. Only five nations have not signed the Chemical Weapons Convention and are therefore unhindered by restrictions on the use of CS gas: Angola, Egypt, North Korea, Somalia, and Syria.[17]
Domestic police use of CS is legal in many countries, however, as the Chemical Weapons Convention prohibits only military use.