In basic training we received classes on lawful and unlawful orders, but once in your regular unit, the message is clear... your team/squad leader, platoon sgt, or first sgt will tell you what to do and you will comply. I don't even recall any heavy emphasis on it in PLDC or BNCOC. The presumption is that your CO is not going to give you an unlawful order. While that doesn't absolve you of responsibility for following an unlawful order, your average joe doesn't have time to brush up on constitutional ethics while doing everything else that you chain of command tasks you with in a day. It's probably both more practical and more effective to keep your company grade officers and NCOs well versed in the implications of unlawful orders. Lower enlisted are always going to do exactly what they are told unless there's a clear problem with the order IE: an order to go kill a room full of babies or set a prisoner on fire.