Can President Trump take us to war in North Korea? That is the existential question. He is commander in chief and he has custody of the nuclear codes. Despite the constitutional provision that only Congress can declare war, what can President Trump actually do?
First, the nuclear codes. A consequence of the long cold war, with both bitter adversaries in possession of large arsenals of nuclear weapons, it was recognized that the time to act in case of an ICBM attack was very limited. Assembling Congress to debate and pass a resolution to declare war was impossible. If this nation were to act in response to a nuclear attack, there are only a few minutes to do so before the nuclear bombs would start to rain down. It was decided to develop an elaborate decision process to provide a check on any errors in information, but ultimately faith had to be placed in a single individual to order the response; that individual is the President of the United States. Missiles will be launched on his order via the nuclear codes; it cannot be countermanded.
However, the nuclear codes and the decision process surrounding them were all worked out in the context of a response to a nuclear attack by an adversary. To exercise the codes without such a context constitutes a “first use of nuclear weapons,” something the citizens of this country have long understood we will never do. We did it in World War II, and in the aftermath we vowed never to do that again. And if we should choose to do a “first use,” there is no constraining time element; we have time to have Congress to debate and decide if this is the thing to do. So there is no rationale to support a president’s unfettered exercise of the nuclear codes in a “first use” scenario.