If there was any question whether White Phosphorous is a banned chemical weapon under the Chemical Weapons Convention, "to which the U.S. is a party", this ought to clear it up:
The CWC is monitored by the Organisation for the Prohibition of Chemical Weapons, based in The Hague. Its spokesman Peter Kaiser was asked if WP was banned by the CWC and he had this to say:
"No it's not forbidden by the CWC if it is used within the context of a military application which does not require or does not intend to use the toxic properties of white phosphorus. White phosphorus is normally used to produce smoke, to camouflage movement.
"If that is the purpose for which the white phosphorus is used, then that is considered under the Convention legitimate use.
"If on the other hand the toxic properties of white phosphorus, the caustic properties, are specifically intended to be used as a weapon, that of course is prohibited, because the way the Convention is structured or the way it is in fact applied, any chemicals used against humans or animals that cause harm or death through the toxic properties of the chemical are considered chemical weapons."
Before I speak too soon, however, we have this caveat, which, though not noble by any measure, needs to be considered in determining whether the CAC has been violated:
The US can say therefore that this is not a chemical weapon and further, it argues that it is not the toxic properties but the heat from WP which causes the damage. And, this argument goes, since incendiary weapons are not covered by the CWC, therefore the use of WP against combatants is not prohibited...the United States has not signed up to a convention covering incendiary weapons which seeks to restrict their use.
This convention has the cumbersome title "Convention on Certain Conventional Weapons." Agreed in 1980, its Protocol III covers "Prohibitions or Restrictions on use of Incendiary Weapons."
This prohibits WP or other incendiaries (like flamethrowers) against civilians or civilian objects and its use by air strikes against military targets located in a concentration of civilians. It also limits WP use by other means (such as mortars or direct fire from tanks) against military targets in a civilian area. Such targets have to be separated from civilian concentrations and "all feasible precautions" taken to avoid civilian casualties.
One can imagine that the use of White Phosphorous was not random, and instead was strategized and ordered, and thus vetted by our ever-clever military legal advisors, with the understanding that it would be best if the use of WP was not to become generally known, but, if it did, there was a fallback legal position.
My take is that it is wrong (if not evil) to use a chemical weapon that indiscriminately melts the skin off anyone unfortunate enough to be in the ordinance zone. I'm not saying this in light of the history of war, which has employed much more savage efforts (including our own use of nuclear weapons), but in the language of right conduct and morality, whether true to Christian or other ideals.