tell that to Lt Bill Calley. The legal principle at play is the "duty to disobey unlawful orders." In the U.S. military, following a superior's order is mandatory, but this obligation only applies to lawful orders. An order is unlawful if it is patently illegal, such as one that directs the commission of a crime or violates the U.S. Constitution or international law (like the laws of war/Geneva Conventions). The My Lai Precedent The My Lai Massacre is the most significant historical case that established the modern legal standard for American soldiers in this context:









