[The Adventures of Buckaroo Banzai Across The 8th Dimension (1984)]

While the need for the president of the United States to respond swiftly to a nuclear emergency is clear, should there be limits on the commander in chief’s authority to order use of nuclear weapons in situations that fall below the threshold of existential threat? The question has arisen because the administration of President Donald Trump has challenged the existing taboos against nuclear use.

Last November, the U.S. Senate Foreign Relations Committee held a hearing to investigate the topic, which congress had not considered since the height of the Cold War in the mid-1970s. Called at the behest of Senator Bob Corker (R-TN), the committee chairman, the hearing appeared intended to address congressional concerns over rumors of consideration of a preemptive U.S. attack on North Korea that could include nuclear strikes.

The consensus of the witnesses called to testify was that as presently construed, there is little statutory limit on the president’s power to authorize nuclear weapon use. The witnesses also questioned the wisdom of legislating changes to the existing setup.

Professor Peter Fever of Duke University, a noted scholar on nuclear issues and former National Security Council advisor, caveated between presidential authority to respond to a “bolt from the blue” surprise nuclear strike by an adversary, which was unquestioned, and the legitimacy of unilaterally ordering the use of nuclear weapons in a non-emergency scenario, which would be far more dubious. He conceded that there is no formal test for legality; the only real constraint would lie in the judgement of U.S. military personnel whether or not to carry out a presidential order of uncertain lawfulness.

There is no existing statutory framework undergirding the existing arrangement; it is an artifact of the urgency of the Cold War nuclear arms race. Under the Atomic Energy Act, congress gave responsibility for development, production, and custody of nuclear weapons to the executive branch, but has passed no laws defining the circumstances under which they may or may not be used. Harry S. Truman alone decided to use atomic bombs against Japan in 1945. In the late-1950s, Dwight D. Eisenhower secretly pre-delegated authority to use nuclear weapons in certain emergency situations to some U.S. theater commanders; these instructions were also adopted by John F. Kennedy and Lyndon Johnson. Several presidents authorized secret deployment of nuclear weapons to overseas storage locations.

The U.S. constitution offers no clear guidance. War power are divided between congress, which has the sole authority to declare war and to raise and maintain armed forces, and the president, who is commander in chief of the armed forces. Congress attempted to clarify the circumstances when it was permissible for the president to unilaterally authorize the use of military force in the War Powers Resolution of 1973. It stipulates that the president may commit U.S. military forces abroad only following a congressional declaration of war or authorization to use force, or in response to “a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.” Successive presidents have held that the resolution is unconstitutional, however, and have ignored its provisions on several occasions.

Congress has traditionally afforded presidents wide deference in the conduct of foreign affairs and military conflicts, albeit under its existing mechanisms of oversight. In waging wars, presidents are subject to U.S. law, including obligations to follow congressionally-approved international conventions defining the laws of war. While the president and congress have disagreed over whether or not to begin or end foreign conflicts, the legislative branch has rarely elected to impose limits on a president’s prerogatives on how to wage such conflicts, to include the choice of weapons to be employed.

The situation in Korea is an interesting case in itself. It was the first post-World War II case where a president committed U.S. military forces to an overseas conflict without seeking a congressional declaration of war. Congress neither authorized U.S. intervention in 1950 nor sanctioned the 1953 armistice that led to a cessation of combat. Truman instead invoked United Nations Security Council resolutions as justification for intervening in what he termed a “police action.”

Legally, the U.S. remains in a state of hostilities with North Korea. The 1953 armistice that halted the fighting was supposed to lead to a formal peace treaty, but an agreement was never consummated. Under such precedents, the Trump administration could well claim that that the president is within his constitutional prerogatives in deciding to employ nuclear weapons there in a case of renewed hostilities.

In all reality, defining the limits of presidential authority over nuclear weapons would be a political matter. While congress possesses the constitutional right to legislate U.S. laws on the subject, actually doing so would likely require a rare bipartisan sense of purpose strong enough to overcome what would undoubtedly be resolute political and institutional opposition. Even if such a law was passed, it is likely every president would view it is an unconstitutional infringement on executive power. Resolving an impasse could provoke a constitutional crisis. Leaving it unresolved could also easily result in catastrophic confusion in the military chain of command in an emergency. Redefining presidential nuclear authority would also probably require an expensive retooling of the nuclear command and control system. It would also introduce unforeseen second and third order effects into American foreign policy and military strategy.

In the end, a better solution to the problem might simply be for the American people to exercise due care in electing presidents to trust with decisions of existential consequence. Or they could decide to mitigate the risk by drastically reducing or abolishing the nuclear stockpile.