The general in charge of America’s nuclear arsenal, John Hyten, recently said he would resist carrying out an illegal order from the president to use those weapons.

His comments echoed the ones made a few days earlier by one of his predecessors, retired Air Force Gen. Robert Kehler. At a Senate Foreign Relations Committee hearing on Nov. 14, Kehler asserted that nuclear operations officers would refuse to implement an unlawful order.

While the generals are no doubt military men of integrity, my four decades of experience as a diplomat and scholar of American foreign policy suggest there is no law that would make a presidential order to launch a preemptive nuclear strike on North Korea illegal.

Here’s why.

No applicable law

Congress has the constitutional responsibility for declaring war, but it has not done so since World War II. That has not prevented every president since then from engaging in military conflicts large and small. Even American participation in the Korean War was not authorized by Congress. So, the absence of a formal declaration of war against North Korea is no barrier to a nuclear strike.

The War Powers Resolution attempted to rein in the president’s prerogatives when it comes to armed conflict. It requires the president to explain to Congress why he is using military force within 60 days of his doing so. But that 1973 law has often been ignored, kicks in only months after military action has been initiated and is considered by some to be unconstitutional.

In recent years, Congress has often acted to allow the president to use military force without a declaration of war. After 9/11, it passed an Authorization for the Use of Military Force to permit the president to go after those involved in the terrorist attacks that day. President Bush used that authorization in his rationale for invading Iraq, even though there was no connection to the attack. President Obama used it during his time in office to justify drone strikes and other military actions. In other words, the 9/11 authorization has been used by presidents to kill people considered terrorists, including American citizens abroad like Anwar al-Awlaki.

Given the lack of congressional restraints, are there other checks on the president’s ability to wage war?

Not just lack of a law

In his congressional testimony, Gen. Kehler stated that the use of nuclear weapons was governed by the “law of war.” According to the Defense Department manual on the subject, the law of war is defined as “that part of international law that regulates the resort to armed force; the conduct of hostilities and the protection of war victims in both international and non-international armed conflict; belligerent occupation; and the relationships between belligerent, neutral, and non-belligerent States.”

The law of war, therefore, amounts to little more than a philosophical discussion and international law and treaties like the Geneva Convention, all of which are not considered an obstacle when a president asserts that protecting national security requires it. The Bush administration ignored these conventions when they wanted to use torture.

Kehler also noted that the Nuclear Posture Review of 2010 provided the context for the use of nuclear weapons. The 2010 review was an Obama-era update of nuclear policy left over from the Cold War. It clarified that policy by stating that the “United States will not use or threaten to use nuclear weapons against non-nuclear weapons states that are party to the Nuclear Non-Proliferation Treaty and in compliance with their nuclear non-proliferation obligations.” North Korea withdrew from the treaty in 2003, and President Donald Trump has repeatedly threatened to “totally destroy” that country with “fire and fury.”

The Washington way

Another reason Trump has no constraints against carrying out those threats is the way Washington works. In his comments at the conference, Gen. Hyten said, “If you execute an unlawful order, you will go to jail.” Not only did none of the senior officials involved in crimes like illegal enhanced interrogation techniques go to jail, they were often promoted. One example is the current deputy director of the CIA who, according to The New York Times, “oversaw the torture of two terrorism suspects and later took part in an order to destroy videotapes documenting their brutal interrogations.”

No one is likely to be punished for carrying out a presidential order that was subsequently deemed illegal. It would not be considered illegal at the time it is given because a president can surround himself with lawyers like John Yoo and former U.S. Attorney General Alberto Gonzales, who had no trouble telling George W. Bush anything he wanted to do was legal. And if someone in the military chain of command refused to carry out such an order, how long would it take for the man who became famous with the phrase “you’re fired” to say just that? After all, he had no hesitation about firing the director of the FBI, James Comey.

In addition, Trump has taken a step that further removes the possibility of a legal constraint. He has added North Korea once again to the list of state sponsors of terrorism. The list has frequently been used for political purposes that have nothing to do with terrorism. That is demonstrated by the fact that the Bush administration took North Korea off the list in an attempt to salvage a deal regarding its nuclear program.

Many might believe that Congress will surely act to impose limitations on the president. They need to read only the first sentence of the Washington Post story on the hearing where Gen. Kehler testified to have that idea thoroughly dispelled.

“Senators trying to prevent President Trump from launching an unprovoked nuclear attack were stymied Tuesday, after a panel of experts warned them against rewriting laws to restrain a commander in chief many worry is impulsive and unpredictable enough to start a devastating international crisis.”

One expert asserted that as commander-in-chief, the president has the sole authority to decide to use nuclear weapons. Another, reflecting a mentality more suited to the Cold War, said constraints might reduce the deterrent value of those weapons.

The bottom line is that a nuclear war won’t be prevented by military officers refusing to obey an order they consider illegal. And such a situation won’t be avoided by congressional action. The legislative branch is paralyzed by partisan politics. Using the bomb is up to the discretion of a president who came to office with no experience in the military, government or foreign affairs beyond real estate deals in other countries. And after ten months of on-the-job training, he seems no better prepared for such a responsibility.