Trump with the nuclear codes is terrifying. But the threat of a first strike is a vital deterrent

President Trump speaks to the media at the White House in Washington on Oct. 16.

Alarmed by President Trump’s bellicose statements and impulsive governing style, two congressional Democrats have introduced legislation that would prohibit the president — any president — from launching a nuclear first strike without a declaration of war by Congress explicitly endorsing such an attack.

We too are dismayed by Trump’s rhetoric, including his threat to rain “fire and fury” on North Korea. We shudder to think about the human consequences of any use of nuclear weapons, even in self-defense, which is why we support arms-control agreements and efforts to prevent nuclear proliferation. We also believe that, as a general matter, Congress needs to be more assertive in exercising oversight over the use of military force.

But we can’t support the Restricting First Use of Nuclear Weapons Act of 2017 proposed by Sen. Ed Markey of Massachusetts and Rep. Ted Lieu of Torrance.

Congress shouldn’t attempt to legislate a drastic change in the president’s authority to defend the nation.

In seeking to restrict the president’s authority to launch a first strike, the bill cites Congress’ authority under the Constitution to declare war. The legislation says that the framers of the Constitution understood that “the monumental decision to go to war . . . must be made by the representatives of the people and not by a single person.”

The problem is that Congress’ authority to declare war has always been in tension with the Constitution’s designation of the president as “commander in chief of the Army and Navy of the United States,” a role that sometimes requires the president to act swiftly to defend the nation. The nuclear age further complicated the relationship between the two branches because decisions about launching a nuclear attack may have to be made under severe time pressure.

Our principal concern about this bill is that it would make it harder for a president not just to use nuclear weapons, but also to deter aggression by leaving adversaries in doubt about whether and when such weapons might be used.

This ambiguity is part of the paradoxical policy of nuclear deterrence that traces back to the Cold War era, in which Soviet military planners contemplating ways to overrun NATO countries’ defenses with tanks and troops had to reckon with the possibility that the U.S. might respond with nuclear weapons. But it still has some relevance today, which is why the U.S. hasn’t committed to “no first use.”

The Obama administration considered, but eventually decided against, making such a commitment. Instead, that administration adopted a policy stating that the U.S, would consider use of nuclear weapons only in certain extreme circumstances. It also promised to strengthen conventional capabilities with the goal of “making deterrence of nuclear attack on the United States or our allies and partners the sole purpose of U.S. nuclear weapons.”

In testimony before the Foreign Relations Committee last week, Brian P. McKeon, a Pentagon official in the Obama administration, said that the Trump administration is continuing to follow the Obama policy while it develops its own approach to nukes.

That would be consistent with Trump’s comments about “first use” during last year’s campaign. In a debate with Hillary Clinton he said: "I would certainly not do first strike. I think that once the nuclear alternative happens, it's over. At the same time, we have to be prepared. I can't take anything off the table."

Of course, many members of Congress — not all of them Democrats — worry that this sort of cautious formulation might give way to a heedless reaction if the mercurial Trump felt provoked.

At the Foreign Relations Committee session, Sen. Chris Murphy (D-Conn.) said he and others were 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 U.S. national security interests.” Even Sen. Bob Corker (R-Tenn.), the chairman of the committee who at least for now opposes legislation to restrict the president in this area, told the New York Times last month that he worried that “we could be heading toward World War III with the kinds of comments that [Trump is] making.” (In the same interview, Corker added that “I don’t believe he is a warmonger.”)

We understand the concerns about Trump’s temperament. Indeed, we share them. But, despite his Twitter rants, the president has deferred to the advice of his national security team, including on nuclear strategy. So long as that is the case, Congress shouldn’t attempt to legislate a drastic change in the president’s authority to defend the nation.