First of all, I completely agree with the minority of posters in this thread who have written things to the effect that the Commander of Strategic Command answered the question in the same way that every other military leader would have, or should have. According to a news report I listened to this morning, General Hyten was directly asked a question to the effect of, “Would you obey an illegal order to launch nuclear weapons?” (I was listening to the radio, so I’m not sure how the question was precisely phrased.) The answer, of course, is No.
It is clear to me that the Constitution invests in the President quite expansive authority to protect the country against harm, so far as the harm is actual and occuring/imminent, as opposed to speculative.
So if a President wanted to launch a nuclear strike on a country that he reasonably believes has launched an attack on us, or appears to be on the verge of doing so, I would conclude that the President most likely has very wide discretion to do so. This is based not only on the Constitution, but also the laws of armed conflict that allow anticipatory self-defense.
But if the President wanted to launch a nuclear strike on a country for which there’s no reason to believe has, or is imminently planning to, attacked the US, then the laws of armed conflict do not afford protection for what’s known as a “preventative war.” (That can be generally defined as, we think someday a country may be a bigger threat to us, so we’re going to attack now while they are still weak.)
Further, neither the Constitution nor the War Powers Resolution give the President the power to launch a war because he feels like it. The power to declare war is reserved to Congress. We can reasonably believe that the power to launch an unprovoked war is a matter entirely within the domain of the decision of Congress whether to do so or not; as there’s no valid argument that the President must take action immediately to forestall a grave threat to our country.
By this logic, if the President decided to order a nuclear attack on North Korea, he would probably have the benefit of doubt on his side… unless military leaders were convinced that North Korea was not doing anything at that moment that made them believe that North Korea was planning an imminent strike on the United States. Absent a reasonable belief on an imminent threat, carrying out an order to launch a nuclear attack on a country that is not related to self defense is quite simply carrying out an order to murder millions of people. But if the evidence was ambiguous as to whether North Korea was preparing for an attack on the United States, the President would probably get the benefit of the doubt.
And to go one step further, if the President were to order a nuclear strike against France, where there is clearly no reason for such an attack, it is unambiguous that such a nuclear attack by the US would be a violation of the laws of war. The scenarios under which the United States could legally carry out an attack on an ally are bizarre to the extreme.