1. Napalm is from from WWII. Maybe get the nomenclature correct.
2. Banned? By whom? International weapons treaties? Signed by whom? Enforced by whom?
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Activists on the ground said the Syrian air force was responsible for the atrocity. The use of Napalm in warfare is effectively banned under international weapons treaties.
The use of napalm against civilians or in areas with dense civilian populations is against international law starting in 1980.
https://en.wikipedia.org/wiki/Protocol_on_Incendiary_Weapons
Strictly speaking Assad did not break the law because Syria never signed the treaty.