Senators held a congressional hearing on Tuesday to discuss the US president’s authority to launch a nuclear strike. It was the first hearing to overtly address this issue in more than four decades.

The hearing was not explicitly about President Trump, but rather about the general question of whether the president currently has too much power over our nuclear arsenal. But the fact that Trump is swapping Twitter insults with North Korea’s Kim Jong Un and has threatened to use “fire and fury” against the regime was clearly a motivating factor.

“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 strike that is wildly out of step with US interests,” said Sen. Chris Murphy, a Democrat from Connecticut.

Even Bob Corker, a Republican senator from Tennessee, warned that Trump’s reckless threats could put the country on a “path to World War III.”

One of the experts who testified at the hearing was Peter Feaver, a political science professor at Duke University and a former special adviser on the National Security Council. I reached out to Feaver with two big questions: Can the president unilaterally launch a nuclear strike? And what are the checks in place to stop an unlawful order from the president?

The answer, it turns out, is complicated. You can read my lightly edited conversation with Feaver below.

Sean Illing

Let me start with a simple but important question: Can the president unilaterally launch a nuclear strike?

Peter Feaver

No. But the wording of your question is very precise. Can he launch a strike “unilaterally”? No. He requires other people to carry out an order, so he can't just lean on a button and automatically the missiles fly. But he has the legal and political authority on his own to give an order that would cause other people to take steps which would result in a nuclear strike. That’s the system we currently have.

Sean Illing

So there’s no magic lever the president can pull to send us into nuclear war, but I’m trying to imagine the contexts in which the president might give the order.

Peter Feaver

Well, there are two that come to mind. One is that the president is woken up in the middle of the night and told he has only 30 minutes or less to make a decision because we are under attack or about to be attacked, and of course that means hundreds if not thousands of people in the national security complex who've been monitoring world events and passed through various protocols have concluded this is what's happening, and we need an answer from the president. In that context, the system is designed to be able to carry out an order in that narrow time span, and he alone would have the legal authority to give that order if he's still alive.

The other scenario is that the president wakes the military up in the middle of the night and says, "Hey, I wanna do a nuclear strike," and in that setting, he would raise a lot of alarms throughout the chain of command. People would be saying, "Well, what is this? Why are we doing this?" It would require a lot more people to say, "Yes. This is the right decision."

Sean Illing

That is somewhat encouraging, but you’re basically saying that even in the second scenario, the only thing that would stop a nuclear strike would be a few soldiers deciding to disobey an order from the president.

Peter Feaver

Well, they're trained to disobey illegal orders, so context matters. If they've woken up the president because they believe they're under attack, there's a presumption of legality if the president orders a strike. But if the president wakes them up in the middle of the night and orders a nuclear strike with no context, no crisis, no alert, then there's not a presumption that that order is legal. They would raise serious questions.

Sean Illing

Still, what you’re saying is that if a reckless or illegal strike was ordered, we’re relying upon the real-time judgment of a few generals to stop it?

Peter Feaver

Basically. The piece you're missing is that in the process of doing this, it would raise lots of alarms throughout the system, so the chief of staff of the White House, the national security adviser, the chairman of the Joint Chiefs of Staff — they would all ask, “What’s happening? We just got this crazy order. What’s going on?”

If they were given reliable information that we’re really under attack, that something is really happening, then you would expect the order to be carried out. But if they’re saying, “We don’t know what’s going on. No one's alerted us," they would likely halt the process and get some clarity.

And remember that time constraints would not be severe under the second scenario, where the president wakes up the military. When the military wakes up the president, then time constraints are very short and there’s not a lot of time to check and double-check. But there's plenty of time in the other scenario, so that means implicitly a lot of people would have to go along with it.

Sean Illing

As you know, there are some people in Congress who are looking to pass a law that would diminish the president’s authority to launch a nuclear strike. Do you think that’s a good idea?

Peter Feaver

I think it's wise to take a close look at nuclear command and control. It's been a while since it's been scrutinized at the level I'm talking about, not just from people inside but also from people outside asking tough questions. I think the time is ripe for that. The threat environment is vastly different today than it was even seven years ago when President Obama conducted a nuclear posture review, and now we've got cyberthreats that are much more severe than when Congress last looked at it.

But to answer your question more directly, I’m wary about looking for simple legislative fixes, because they're not likely to work and also because they’re likely to have unintended consequences that we’d have to think through

Sean Illing

Why wouldn’t legislative solutions work? And what sort of unintended consequences are you worried about?

Peter Feaver

Well, I don't think you're going to pass a resolution that requires the president to get a vote from Congress. First of all, I don't think Congress is going to pass a law that would be that severe. Throughout the Cold War they never passed that law, and I see no reason to think they would pass it today.

Second, there would be grave doubt whether Congress could act in times of crisis. The law would almost certainly have to be written so as to leave substantial discretion up to the president. In times of crisis, this law doesn't apply. In times of urgency, this law doesn't apply. In other words, you are reproducing some of the same discretion and reliance on the good faith and professionalism of the people implementing it in order for even that law to work.

Sean Illing

Do you have any suggestions about what we can or should do short of major legislative solutions?

Peter Feaver

There are several ideas that are worth considering. I think in some cases they would just codify what is de facto practice, namely that the president should be consulting with his national security team, which I think is already the practice, but it would not hurt to make that more explicit. That's not affecting the chain of command, per se. That's just clarifying that the president should be seeking advice and counsel when time permits.

But here’s the thing: There really is no way around the human element. Hardware is trumped by software, hardware being the technology and software being the rules and procedures that govern it. But software is trumped by wetware, which is the human element. The human element is the key element, and the professionalism of the senior commanders and the president's advisory team will always be a crucial part of the picture.

Sean Illing

Are you confident that the structures and the systems and the protocols that we have in place are sufficient to guard against an accidental nuclear conflict or an irresponsible deployment of nuclear weapons?

Peter Feaver

I think the systems are pretty good, but no system is so good that it wouldn't benefit from a close scrutiny and a full review, and I think a full review is overdue, for all the reasons I mentioned earlier in our interview. This is definitely not a “Nothing to see here, move along” scenario. There are real concerns, and we need to look closely at them.

On the other hand, I've read very carefully the most dire warnings of some of the specialists, and I think they are based on some misleading conflations of different contexts. They describe how the system works in a crisis and then wrongly state that this is how it would operate if the president woke up in the middle of the night and wanted to do something, and of course that's not true. It would not operate that way if the president went to the military and called for a nuclear strike. So I do think some of the worst fears have been overstated.

Sean Illing

So we needn’t be terrified by the prospect of President Trump deciding, on a whim, to fire a nuclear missile?

Peter Feaver

It’s a legitimate concern — I don’t want to dismiss it. But there are more checks in place than people realize. And while the system needs serious reconsideration, I’m not telling my family to start stocking water and canned foods in preparation for a nuclear winter.