Senate hearings to confirm a Supreme Court justice, to determine the extent of the Trump campaign’s possible coordination with Russia and to exercise oversight of the Justice Department (which is under unique pressure and challenge from a president who does not grasp the necessity of a Justice Department free from politicization) have been both gripping and essential to protect the country from President Trump’s anti-democratic impulses. Nevertheless, the most consequential one of the year took place in the Senate Foreign Relations Committee hearing on Tuesday in which three knowledgeable and thoughtful witnesses — Peter Feaver, retired Gen. C. Robert Kehler (who previously was responsible for U.S. Strategic Command) and the former acting undersecretary for policy at the Defense Department, Brian McKeon — held forth on the topic of presidential authority to initiate nuclear war.

The questions were sober, nonpartisan and effective in teasing out a number of critical points. Most clearly, the president alone has authority to respond to a nuclear attack or an imminent nuclear attack. While the definition of imminent (a foe’s mere possession of a nuclear weapon, the witnesses said, would not create an imminent threat) is debatable, our constitutional system does not allow for Congress or other civilian authorities to usurp or limit the commander in chief’s power.

However, when discussing a preemptive, strategic use of nuclear weapons (e.g. Trump thinks negotiations are a waste and decides one morning to nuke Pyongyang), a number of considerations come into play.

First, as with all orders, the military must carry out only legal orders. Kehler in his written testimony explained:

The law of war governs the use of US nuclear weapons. Nuclear options and orders are no different in this regard than any other weapon. Here, US policy as articulated in the 2010  Nuclear Posture Review (NPR) provided important context regarding the consideration of US nuclear use (i.e., extreme circumstances when vital national interests are at stake). The 2010 NPR also restated the “negative security guarantee” (i.e., the US will not consider using nuclear weapons against any non-nuclear weapons state that is party to the Nuclear Nonproliferation Treaty and in compliance with their nonproliferation obligations). In addition, the legal principles of military necessity, distinction, and proportionality also apply to nuclear plans, operations, and decisions. Legal advisors are deeply involved with commanders at all steps of the deliberate and crisis action processes to offer perspective on how force is to be used as well as the decision to use force.

That requires that the military determine whether the person directing use of nuclear weapons has legal authority to issue the order and also to determine whether that order meets with the law of war (military necessity, distinction and proportionality). The witnesses were in agreement that first-strike use of nuclear weapons outside the case of imminent attack is an act of war that should require congressional authorization. If Trump were to proceed without Congress, military commanders might question his authority to act in the absence of Congress.

Second, the military process is designed to be robust, to involve lawyers up and down the chain of command and to put in place as head of Strategic Command a four-star general with decades of decision-making experience. Kehler said in his experience he would not have had a problem saying, “Wait. I need time to determine whether this is legal.”

Third, the witnesses also agreed that it is likely impossible to craft legislation that could constitutionally limit the president’s power to launch a first strike without limiting the deterrent effect of our nuclear arsenal. That means the safeguards to prevent a disastrous decision to begin nuclear war remain human and not legal. Congress must insist on its power to declare war. The defense secretary must recommend the most qualified and sage person available as head of Strategic Command. Every member of the military and the lawyers who operate in all branches, at the National Security Council and elsewhere, must be well versed in the law of war and feel empowered to delay — and if need be, reject — an illegal order. This is the antithesis of Trump’s notion that whatever order he gives will be followed blindly. That is not how the American system works.

Certainly, orders carry the presumption of legality, and every soldier cannot be a lawyer in the foxhole. Our enemies and friends alike must believe that we have the means and will to use nuclear weapons — in order to make their use less likely. Nevertheless, the hearing should give Americans greater confidence that Trump cannot wake up one day, decide to nuke “Rocket Man” and expect those orders to be swiftly carried out without challenge. That’s some consolation.

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However, the real problem here is that the American people — urged on by people such as Sen. Marco Rubio (R-Fla.), who sits on the foreign relations panel and endorsed Trump but could not during the campaign say he would trust Trump with the nuclear codes — invested the power of commander in chief in a man entirely unfit for the position, whose judgment, intellect and temperament do not inspire confidence.

To Republicans still insisting that Hillary Clinton would have been worse, we can only say that we would not have worried about her power to order use of nuclear weapons. With Trump, anyone not worried about his power to use nuclear weapons is delusional. By the same token, Trump’s ability outside of an actual or imminent attack (which itself would be identified by military commanders) to take cataclysmic action on his own is not as unlimited as one might expect. For that, we can be grateful.

If nothing else, the hearing should serve to emphasize the necessity of a military steeped in the tradition of constitutional law and the law of war, confirmation of only the most esteemed senior executive branch employees and a Congress that will not neglect its role as a coequal branch of government. It also should remind voters that elections are not primal scream therapy, but selection of the individual who will possess frightful power.