I'm glad to see people are talking about the white phosphorus matter. Chuy has a good post on it, for instance, and I want to continue this conversation.
There are some issues in the conversation that everyone seems to be harping on, but that I don't think are particularly relevant here. The first is the semantic argument over whether WP qualifies as a "chemical weapon." I don't find this enlightening or relevant because, though the use of chemical weapons is illegal, the use of incendiaries against people is arguably unethical for the exact same reasons: namely the gruesomeness of the injuries and the lack of precision targetting.
Same thing with the use of WP against civilians. As odd as that sounds, my point is that the use of any weapon against civilians is a big no-no, so if civilians were attacked then the fact that it was WP is immaterial. It would be just as bad if it were conventional bullets and bombs.
The civilians angle is only relevant (and even then, obliquely so) in the matter of the use of WP against personnel, which I think is really the crux of the WP issue. In a quasi-guerilla war such as this, where insurgents are often mixed among the populace, using a weapon that ignites everything within a certain radius is likely to hit some civilians. This is a concern, for sure, but bombs have the same drawback, and few people cry foul in that case.
The issue is whether or not WP was used against insurgents as more than solely "illumination" (which the military admits it was), and the ethics of that decision. As I said earlier, it seems that incendiary weapons have similar drawbacks to chemical weapons, which are illegal to use against personnel. I also understand that army artillerymen are taught not to use it except for purposes of illumination, so apparently the army normally considers the use of WP against personnel to be a bad idea.
I imagine one of the reasons, which we are now experiencing firsthand, is the potentially catastrophic effect on PR caused by pictures of corpses partially melted by WP. And in the new age of warfare, where the war of ideas and reputation is considered by military experts to be equally important to the actual physical combat, PR is a very serious matter.