also, we should nuke the brown people.
in reality, the reason there's a law of war is to remove unnecessary suffering. poison gases, napalm, nuclear attacks, they all cause unnecessary suffering. no side wants wounded soldiers returning home with wounds that will cause them grief and misery throughout their lives.
ADDENDUM: before you ask why don't terrorists follow the laws of war, that's because they're TERRORISTS. they use any method available to cause terror and dissent.