The use of weapons that poison, or that spread disease, has been considered unacceptable for centuries, as we know from ancient codes of warfare. But it was public abhorrence of chemical warfare in the First World War that led to a specific international ban on the use of chemical and biological weapons in 1925. States further strengthened this prohibition with agreement of the
Biological Weapons Convention in 1972 and the
Chemical Weapons Convention in 1993. We must work to ensure that chemical and biological weapons are completely eliminated, that they are not used again, and that they are never reacquired. The prohibitions on the use of these weapons are now part of customary international humanitarian law, which means they apply to all parties to all armed conflicts even if they have not joined the treaties.
Chemical weapons: An absolute prohibition under international humanitarian law - ICRC
A CBRN incident differs from a
hazardous material incident in both effect scope (i.e., CBRNe can be a mass casualty situation) and in intent. CBRN incidents are responded to under the assumption that they are deliberate, malicious acts with the intention to kill, sicken, and/or disrupt society.
Trovo sia corretto individuare un salto di qualità tra l'utilizzo di armi convenzionali e armi chimiche, il che non esclude abusi a fini propagandistici.