On Tuesday morning, the Senate Committee on Foreign Relations held a hearing on the US President’s authority to launch nuclear weapons.

The hearing was the first of its kind in 41 years and a time for Senators on the committee to ask a panel of expert witnesses about the protocols for launching nuclear weapons.

“We need to revisit the question of whether a single individual has the right or authority to order a nuclear strike under any circumstances,” Maryland Senator Ben Cardin said at the hearing.

Although the chairman of the committee, Republican Tennessee Senator Bob Corker, said in a statement that the hearing was held to clarify “questions about the authorities of the legislative and executive branches with respect to war making,” other Senators were much more candid.

“We are concerned that the president of the US is so unstable, so volatile, and has a decision making process that is so quixotic, that he might order a nuclear strike that is outside the national security process,” Tim Kaine, a Democratic Senator from Virginia, said during the hearing.

Anti-nuke protesters at the congressional hearing. Screengrab: C-span

Indeed, President Trump has made a habit of speaking flippantly about waging nuclear war with North Korea on Twitter in recent weeks. His comments included referring to Kim Jong-un as “little rocket man” during a visit to the United Nations, as well a suggesting that North Korea “won’t be around much longer,” which the North Korean government saw as a “clear declaration of war.” A month earlier, Trump tweeted that “military solutions are now fully in place, locked and loaded, should North Korea act unwisely.”

Many Senators said they have seen an increase in concerns about nuclear war among their constituents following Trump’s talk of military engagement with North Korea. The burning question on their minds, and the minds of many Senators at the hearing, is whether Trump actually has the authority to launch a nuclear attack, and if so, whether it is advisable to pursue legislation that will reign in this authority.

To answer these questions, the Foreign Relations Committee summoned three expert witnesses: General Robert Kehler, a former commander of the United States Strategic Command, Peter Feaver, a professor of political science at Duke University, and Brian McKeon, the former acting undersecretary for policy at the Department of Defense.

Bob Corker, chairman of the Senate Committee on Foreign Relations. Screengrab: C-span

Although the committee’s chairman Senator Corker commented multiple times on how “balanced” the expert panel was, it was difficult to see what was being balanced. As was made explicit at the end of the hearing, all three witnesses were in agreement that legislative action to limit the President’s nuclear authority would be inadvisable. The reason, they argued, is that limiting the President’s authority could curtail the United States’ ability to respond effectively to nuclear threats, thus lessening the deterrents to nuclear war.

As was made clear throughout the hearing, the President has the sole authority to order a nuclear attack under the Atomic Energy Act of 1946. This means that if a country launches nuclear weapons toward the US, the President can order a retaliatory strike without the permission of Congress, whose approval is usually needed for the US to enter into war.

“Every single word that was uttered here is going to be analyzed in Pyongyang,” Idaho Senator James Risch said during the hearing in a direct address to the Hermit Kingdom. “I want to make sure that Pyongyang understands that these decisions [to launch nukes] have to be made in moments and it’s not going to be made by courts, lawyers or Congress. It’s going to be made by the Commander-in-chief of the armed forces.”

This Atomic Energy Act was created in the aftermath of Hiroshima and Nagasaki, and was meant to act as a check to the military, which would presumably want to use nuclear weapons more often. It went unchallenged during the Cold War, when the Soviet Union had the capability of hitting the US with nuclear missiles in under 30 minutes. This meant the ability to order an immediate counter attack was a cornerstone of Mutually Assured Destruction (MAD), a 60s-era theory of warfare that aimed to prevent nuclear war by ensuring that a nuclear conflict would result in the destruction of both the US and USSR.

Today, the MAD theory also basically guides US policy toward other countries with nuclear weapons, even though most only have a handful compared to the US and Russia. (Each have several thousand nuclear warheads.) In this sense, US nuclear war policy might be best described as: ‘Launch even a single warhead in our direction and we’ll turn your entire country to glass.’

But the more pressing question on many of the Senators’ minds was whether Trump has the authority to order a preemptive “first strike.”

“A President launching a preemptive nuclear war against another country is really what’s of the most concern to the American people,” Democratic Massachusetts Senator Edward Markey said. “No one person should have that power.”

Unlike a situation where nuclear warheads are in the air headed toward the US, leaving only minutes to act, a preemptive strike allows for more deliberation and input from a President’s advisors and military lawyers.

“It wouldn’t be the President alone persuading a single military officer on the other side of the telephone,” said Feaver. “There’d be a large group of legal advisers weighing in on this. That’s an important part of the context that’s often lost in the media coverage.”

Senate Committee on Foreign Relations hearing on President's Nuclear Authority. Screengrab: C-span

Bruce Blair, a nuclear policy researcher at Princeton and former member of the nuclear launch control officer with the Air Force who was not at the hearing, disagreed.

"The witnesses suggested that there are checks and balances in the form of legal guidelines and so forth that in my view are really not going to operate," Blair told me on the phone after the hearing. "Often in exercises and in the real world the key advisers fail to report in to provide a potential check and balance in terms of advice. I think the the president would burn through all the resistance under almost all circumstances and assert his authority."

The more sticky part of this question is whether the President requires Congressional approval to launch a nuclear weapon. On the one hand, the President is the only person with the authority to order a nuclear strike, but on the other hand Congressional approval is needed to declare war, and it’s hard to imagine a scenario when launching a nuke wouldn’t also be considered an act of war by the country on the receiving end.

During the hearing, the issue of when a first strike would be justified without Congressional approval seemed to boil down to what constituted an “imminent threat” of an attack.

"A lot of people think that the President has the authority to use his own judgment to decide what presents an imminent strike and that he has the authority to use nuclear weapons to preempt that attack before it gets under way," Blair said. "It's a big area of controversy."

The question of whether there is a legal protocol for determining what constitutes an “imminent threat” that might justify a first strike was explicitly raised by Senator Kaine and Arizona Republican Senator Jeff Flake. It’s a tough and important question. North Korea, for instance, has tested nuclear weapons and has made threats to the United States. Does this constitute an imminent threat, or do the missiles need to be on the launch pad and pointing in America’s direction before a first strike is warranted?

When these questions were raised at the hearing, both General Kehler and Feaver responded by saying: “I’m not a lawyer.”

“Context matters here,” Kehler said. “In a range of scenarios where nuclear weapons use is possible, US policy has helped clarify under what circumstances we’d expect to use nuclear weapons.”

In particular, Kehler cited the Department of Defense’s 2010 nuclear posture review, which paints a broad picture of US nuclear policy. In this review, an imminent threat is characterized as “extreme circumstances when vital national interests are at stake.” That is still a pretty vague definition and would likely be up to military lawyers to decide based on the specific context. According to Kehler, this is partly why every general has a military lawyer by their side these days.

McKeon, who was formally trained as a lawyer, was more to the point in his response.

“The mere possession of a nuclear weapon would not meet that test [of an imminent threat],” McKeon said. “There’d be time required for a congressional authorization if the decision were taken that the mere possession of a nuclear weapon by a state such as North Korea was unacceptable to US national security interests.”

Moreover, the expert panel suggested that a blanket ban on first strikes could be detrimental to the United States’ “calculated ambiguity.” This is military-speak for intentionally not being clear on some policy issues, like whether or not the US would ever deploy nuclear weapons first, as a way of keeping adversaries in the dark and gaining strategic advantage.

Peter Feaver, a professor of political science and public policy at Duke University at the hearing. Screengrab: C-span

Many of the Senators present didn’t seem to be satisfied with this answer, particularly Massachusetts Senator Edward Markey. Markey has been calling for a blanket ban on first strikes for years and his positioning during the hearing made it clear he had no intention of giving up his crusade.