This wee tidbit from Think Progress appears to say that when it comes to deciding whether white phosphorus is a chemical weapon or a particularly foul incendiary weapon--when used against people rather than as a smoke screen or target marker--that Pentagon likes to have it both ways. If used by our "enemies" against our friends WP is a WMD, a proscribed chemical weapon, but used by us against our enemies it is a venerable incendiary device. What changes, of course, is not the chemical structure of whie phosphorus but our relationship to it and all it represents--recognizing, or course, that humans fire the rounds.
I don't care whether white phosphorus is classed as a chemical weapon or an incendiary device or any other euphemysemeemweapon, because in essence, its use as a weapon intended to kill and maim is beyond the pale. I seem to recall an old adage that goes like this: If you adopt the tactics and methods of your enemy in order to defeat him, you also defeat yourself, for you are then your own enemy.