When Lincoln, one of the first fathers of the barbarism of Total War, declares something is barbaric to him, you have to pay attention.
Glenn Greenwald of Salon heartily offers an opinion about US killings off-battlefield
The law of war does not allow proclaiming either an individual belonging to the hostile army, or a citizen, or a subject of the hostile government, an outlaw, who may be slain without trial by any captor, any more than the modern law of peace allows such intentional outlawry; on the contrary, it abhors such outrage. The sternest retaliation should follow the murder committed in consequence of such proclamation, made by whatever authority. Civilized nations look with horror upon offers of rewards for the assassination of enemies as relapses into barbaris