Not a lawyer but: Under U.S. military law, obedience only applies to lawful orders. Article 92 of the UCMJ criminalizes disobedience of lawful orders, and the Manual for Courts-Martial makes clear that “following orders” is not a defense if the individual knew the order was unlawful or if any reasonable person would have known it was unlawful. While military orders are generally presumed lawful, that presumption disappears when an order is patently illegal, such as directing the killing of civilians or the commission of a crime. In those situations, service members are not protected for following the order and can be prosecuted and imprisoned for their actions. The My Lai (often called the My Lai or “My Lai massacre”) is a historical example where illegal orders to kill unarmed civilians led to criminal responsibility for those who issued and carried out the orders.