The first is distinction. "In order to ensure respect for and protection of the civilian population and civilian objects, the Parties to the conflict shall at all times distinguish between the civilian population and combatants and between civilian objects and military objectives," Article 48 of the Geneva Conventions, Additional Protocol 1, says. Article 85 describes making the civilian population or individual civilians the object of attack as a grave breach, which is considered a war crime. Nuclear weapons do not distinguish between civilians and combatants.
Another guiding principle is proportionality. "Loss of life and damage to property incidental to attacks must not be excessive in relation to the concrete and direct military advantage expected to be gained," according to the US Army Field Manual FM27-10: Law of Land Warfare. The damage a US nuclear weapon would inflict -- the deaths of hundreds of thousands of people -- would vastly exceed the military object of destroying North Korea's nuclear weapons.
Military necessity is also a well-established law of war. It allows "those measures not forbidden by international law which are indispensable for securing the complete submission of the enemy," according to the Lieber Code. It is never necessary to use a nuclear weapon, except in certain hypothetical cases of self-defense if the survival of the US were at stake.
Finally, there is the principle of unnecessary suffering. "It is prohibited to employ weapons, projectiles and material and methods of warfare of a nature to cause superfluous injury or unnecessary suffering," according to Article 35.2 of the Additional Protocol I to the Geneva Conventions. A nuclear attack on North Korea would kill and maim untold numbers of people.
If the president ordered a nuclear strike, Gen. Hyten said he would offer legal and strategic advice, but he would not violate the laws of war simply on the president's say-so.
Who's in the Nuclear Chain of Command?
Last month, Senate Foreign Relations Committee Chairman Bob Corker (R-Tennessee) worried that Trump may be leading the United States "on the path to World War III." On November 14, Corker convened the first congressional hearing on the president's power to use nuclear weapons since 1976.
Sen. Chris Murphy (D-Connecticut) said, "We are concerned that the president of the United States is so unstable, is so volatile, has a decision-making process that is so quixotic that he might order a nuclear weapons strike that is wildly out of step with US national security interests."
Ret. Gen. Robert Kehler, former commander of the US Strategic Command, testified at the hearing that the military can refuse to follow what it views as an illegal order, including an order to launch a nuclear strike. To be lawful, an order must come from a source with legal authority and must be legal under the law of armed conflict, Gen. Kehler added.
Duke University Professor Peter Feaver testified that the president does not simply press a button to launch nuclear weapons. He can only give an order to others, who would then cause "missiles to fly."
However, although he cannot "press a button," the president has considerable power to manipulate circumstances in ways that would allow him to launch those missiles. Brian McKeon, senior policy adviser in the Pentagon in the Obama administration, testified that if a commander balked at carrying out a launch order, the president could tell the secretary of defense to order the reluctant commander to launch the missiles. "And then, if the commander still resisted," McKeon added, "you either get a new secretary of defense or get a new commander." One way or another, McKeon said, the president would get his way.
Moreover, Bruce Blair, former nuclear missile launch officer and cofounder of the anti-nuclear group Global Zero, told the Associated Press that a president can send a nuclear attack order directly to the Pentagon war room. From there, Blair said, that order "would go to the men and women who would turn the launch keys."
William Perry, secretary of defense in the Clinton administration, concurs. Perry told Politico that defense secretary James Mattis could not necessarily stop a nuclear launch order. "The order can go directly from the president to the Strategic Air Command," Perry said. "So, in a five- or six- or seven-minute kind of decision, the secretary of defense probably never hears about it until it's too late."
Ranking Senate Foreign Relations Committee Member Ben Cardin (D-Maryland) advocated congressional reassertion of authority. He said they should not trust the generals or a set of protocols to act as a check on the president, or rely on individuals hired by the president to resist an illegal order.
"Donald Trump can launch nuclear war as easily as his Twitter account," Cardin cautioned.
Reaffirm Congress's Constitutional War Powers
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