Lots of bloggers talk about the Geneva Conventions, but no one ever links to them (and that's Conventions, plural; they encompass about a half-dozen different treaties and protocols enacted over the last 150 years, starting in 1864). Here's a good primer from two years ago on the history of international law, the development of the concept of "war crimes" and how they apply to the post-9/11 world, in Slate. Originally proposed by the International Red Cross and the Red Crescent in the mid-19th Century, and enacted by the U.S. Senate in the aftermath of the Civil War, its essence is empathatic: we treat enemy combatants in a manner we would demand that our own be treated, no matter how just our cause or how wicked our adversary. Unfortunately, the Geneva Conventions have always seemed to be adhered to only in the aftermath of war, and forgotten when the next conflict starts up. That may be an inevitable outcome of battle, but it is one that we should always keep in mind before the next war starts.