I assume this is all of a result of belonging to the Geneva Convention, however, what if the order is given against a nation that is a non signatory to the Geneva Convention? Is it still applicable?
Sans treaty, Geneva included, a strike (conventional or otherwise) is officially legal. However, I suspect many up and down the chain of command would issue strong opinions on a nuclear strike against, say, Botswana.
Yes - that is exactly the risk an officer faces - courts martial for failing to follow order vs courts martial for following an illegal order. RHIP/RHIR - Rank has it’s privileges/Rank has it’s responsibilities.
It’s true the the Defense department adopted the Nuremberg principals in 1953 as official policy. However, it goes way before the Geneva Convention even before the original US oaths were enacted.
Predecessors include the 1896 Hague Convention, 1861 Lieber Code, etc.
When Officers were first expected to discern what is legal/illegal isn’t well established. However, lower ranking officers since antiquity have long been expected to uphold their allegiance to their sovereign and refuse to comply, report, or otherwise resist senior officers that were disobeying, plotting treason, or otherwise resisting the sovereign.
Post WWII/Korea things have gotten more muddled as the expectation now, despite the oath, is that enlisted (especially NCOs) should push back as well when it is clearly onerous.
The examples of note here are the prosecutions after My Lai. There the enlisted were still courts-martialled despite having “followed orders”.