That said, according to the UCMJ, the orders given to slaughter civilians in Vietnam were unlawful and a soldier refusing to obey them would not have been prosecuted.
"Obedience to orders. It is a defense to any offense that the accused was acting pursuant to orders unless the accused knew the orders to be unlawful or a person of ordinary sense and understanding would have known the orders to be unlawful."
http://jsc.defense.gov/Portals/99/Documents/MCM2016.pdf?ver=...
https://en.wikipedia.org/wiki/Hugh_Thompson_Jr.
https://web.archive.org/web/20120324030925/http://www.usna.e...