Googling "Is napalm legal" produced: <<
Napalm was banned by United Nations convention in 1980, but the US never signed the agreement. Use of Mark-77 fire bombs is considered
legal by the US
...>>
www.smh.com.au/articles/2003/08/08/1060145828249.html
and
The proposed reservation of the United States would revise the
legal ... Incendiary agents such as
napalm and phosphorus are not considered to be CW agents
...
www.globalsecurity.org/military/systems/munitions/incendiary-legal.htm
or
The use of firebombs “remarkably similar” to
napalm is perfectly “
legal”, and the use of white phosphorus as a weapon is totally “legitimate”.
...
www.yirmeyahureview.com/articles/napalm_phosphorus_iraq.htm