In the United States, we do not just elect a president. We elect a commander-in-chief, and the Constitution grants that person tremendous power to protect and defend the nation. In doing so, the founding fathers entrusted an awesome responsibility to our electorate. No burden on the American president is greater than the authority to use nuclear weapons in defense of the nation. The U.S. nuclear arsenal, as well as the command and control system that surrounds and supports it, is designed to protect the United States and its allies from the most severe and catastrophic threats that are unresolvable through any other measure.

For this reason, the president is granted extraordinary authorities regarding the use of these weapons. But these authorities are not boundless, nor should they be. These authorities depend on context and are constrained by law and policy. Only the president can authorize the use of nuclear weapons, and a rigorous process and protocol exist to ensure that he or she can do so appropriately. These well-practiced procedures and mechanisms are designed to ensure that the president has all necessary information and the best advice from legal experts, military commanders, and civilian leaders, when these extraordinary circumstances arise.

The confidence that the president can and will act under such circumstances is no less important to nuclear deterrence than the weapons themselves. Weapons that cannot or will not be used reliably and responsibly cannot deter. At the same time, there must be confidence among all who follow in the chain of command that the order to launch such a weapon is legal and legitimate. At the end of the day, the authority, but most importantly the responsibility and accountability, for the use of U.S. nuclear weapons rests solely with the president. It is a burden the president must carry, not one to slough off to “the generals.”

First and foremost, nuclear policy, doctrine, and procedures are designed to ensure that these weapons will not be used without the full, expressed, and carefully considered authorization and accountability of the president. It is, in fact, a constraining policy, supported by a vast network of personnel, procedures, facilities, equipment, and communications. These powers are not designed to embolden a president to use nuclear weapons, but rather to ensure that these weapons can be used when necessary and appropriate.

The system is also designed to ensure that these weapons can be used under the direst and most time-constrained circumstances imaginable — when the United States or its allies are under imminent attack and our way of life would be threatened absent immediate action. Normally, this is considered plausible only in response to a nuclear attack, although throughout the Cold War the United States considered the prospect of a nuclear response to an overwhelming conventional assault on our NATO allies. This option was solely defensive and a last resort, as it remains today. If such urgency and severity do not exist, the legitimacy of employing nuclear weapons could be called into serious question.

Under Article II of the Constitution, the president is the commander in chief of the nation’s armed forces, which today includes both conventional and nuclear forces. Even the 1973 War Powers Resolution, which represents an attempt by Congress to constrain the president in terms of the use of force, fully recognized that extraordinary circumstances requiring rapid military response could exist, including circumstances that might lead to a nuclear conflict. In such instances, the law permits the president to act quickly and notify Congress after the fact. The legal authority to use the nation’s nuclear arsenal is treated no differently than the use of the vast conventional capabilities at the president’s disposal, and the role of Congress in authorizing or approving such action is the same as with any conventional military action — no more and no less.

Decisions to use nuclear weapons are not above or immune from the law. The use of America’s military might, including its nuclear weapons, has always been governed by the U.S. Constitution and shaped by the laws of armed conflict. The active consideration of factors such as proportionality and the mitigation of civilian casualties are reflected in law and remain critical in considering the use of nuclear weapons, just as they would govern the use of force in conventional conflict. It is difficult to see how the pre-emptive first-use of a nuclear weapon against targets for which plausible conventional options exist — in a crisis that unfolds over weeks and months, as opposed to minute and hours — and against an adversary of vastly inferior capability would meet many of the tests of necessity and legitimacy and therefore garner support from those charged with providing the president with best military and legal advice.

Can a president order the use of nuclear weapons against the advice and counsel of those charged with providing it? Yes. Would such an order be followed? Almost certainly. But a president who overrules such advice and chooses to unleash such an attack would be forced to reckon with Congress, the American people, and even the world the day after. And those senior officers who transmit such an order down through the chain of command would not be immune from scrutiny.

To put it mildly, context matters.

In the current context, the president, members of Congress, and U.S. citizens must consider the following questions before using nuclear weapons:

Is the crisis at hand a matter of such urgency that using time for debate, consultation, negotiation, and diplomacy places vital U.S. interests at unacceptable risk?

Is the magnitude of the crisis so severe that the risks cannot be addressed through conventional military capabilities, and the United States can only protect its interests or citizens by using the most powerful weapons the world has ever known?

Is the crisis so urgent and extraordinary that the use of a nuclear weapon could be considered reasonably proportional and the target appropriate and essential for the nation’s self-defense?

The answers to such questions are principally matters of judgment, but they can also become matters of legality and legitimacy if the fundamental principles that shape our laws, policies, and plans are ignored. Failure to appropriately consider these factors and ensure a legal basis for action could raise questions about the lawfulness of an order, placing at serious jeopardy not only the crisis at hand but also the broader system of nuclear command and control that has deterred our enemies and protected Americans and our allies for more than 70 years. If the answer to these questions is clearly no, then the nation’s security is best served by focusing on the range of non-nuclear options in the president’s toolkit. Employing the most destructive weapons on the planet should be reserved for the extraordinary circumstances that would warrant their use.

Rebecca Hersman is director of the Project on Nuclear Issues and senior adviser for the International Security Program at the Center for Strategic and International Studies. Ms. Hersman joined CSIS in April 2015 from the Department of Defense (DOD), where she served as deputy assistant secretary of defense for countering weapons of mass destruction (WMD) since 2009. In this capacity, she led DOD policy and strategy to prevent WMD proliferation and use, reduce and eliminate WMD risks and respond to WMD dangers. Prior to joining DOD, Ms. Hersman was a senior research fellow with the Center for the Study of Weapons of Mass Destruction at the National Defense University from 1998 to 2009.