https://en.wikipedia.org/wiki/Adamsite
Adamsite or DM is an organic compound; technically, an arsenical diphenylaminechlorarsine, that can be used as a riot control agent. DM belongs to the group of chemical warfare agents known as vomiting agents or sneeze gases.
I think that we can probably consider this a vomiting agent, same sort of idea.
The CWC is comprehensive in the toxic chemicals it regulates.
- The definition of “toxic chemicals” under Article 2.2 includes chemicals that cause “temporary incapacitation”.
- Under the Convention, the use of such “toxic chemicals” would be forbidden unless employed for “purposes not prohibited” and as long as the “types and quantities” are consistent with such purposes.
- Among the “purposes not prohibited” is: “law enforcement including domestic riot control”.
I don't think that use of a tripwire trap could reasonably be domestic riot control, so that's probably in violation of the Chemical Weapons Convention.
Now, that's just a treaty, not customary international law, so it doesn't bind states not party to the treaty.
https://en.wikipedia.org/wiki/Chemical_Weapons_Convention
There are 193 states party to the treaty, but "Four UN states are not party: Egypt, Israel, North Korea and South Sudan." For them, use would be acceptable.