One of us was appointed commandant of the Marine Corps by President Ronald Reagan; the other served as a lawyer in the Reagan White House and has vigorously defended the constitutionality of warrantless National Security Agency wiretaps, presidential signing statements and many other controversial aspects of the war on terrorism. But we cannot in good conscience defend a decision that we believe has compromised our national honor and that may well promote the commission of war crimes by Americans and place at risk the welfare of captured American military forces for generations to come.

The Supreme Court held in Hamdan vs. Rumsfeld last summer that all detainees captured in the war on terrorism are protected by Common Article 3 of the 1949 Geneva Conventions, which prescribes minimum standards of treatment for all persons who are no longer taking an active part in an armed conflict not of an international character. It provides that "in all circumstances" detainees are to be "treated humanely."

This is not just about avoiding "torture." The article expressly prohibits "at any time and in any place whatsoever" any acts of "violence to life and person" or "outrages upon personal dignity, in particular, humiliating and degrading treatment."

Last Friday, the White House issued an executive order attempting to "interpret" Common Article 3 with respect to a controversial CIA interrogation program. The order declares that the CIA program "fully complies with the obligations of the United States under Common Article 3," provided that its interrogation techniques do not violate existing federal statutes (prohibiting such things as torture, mutilation or maiming) and do not constitute "willful and outrageous acts of personal abuse done for the purpose of humiliating or degrading the individual in a manner so serious that any reasonable person, considering the circumstances, would deem the acts to be beyond the bounds of human decency."

In other words, as long as the intent of the abuse is to gather intelligence or to prevent future attacks, and the abuse is not "done for the purpose of humiliating or degrading the individual" — even if that is an inevitable consequence — the president has given the CIA carte blanche to engage in "willful and outrageous acts of personal abuse."

It is firmly established in international law that treaties are to be interpreted in "good faith" in accordance with the ordinary meaning of their words and in light of their purpose. It is clear to us that the language in the executive order cannot even arguably be reconciled with America's clear duty under Common Article 3 to treat all detainees humanely and to avoid any acts of violence against their person.

In April of 1793, Secretary of State Thomas Jefferson wrote to President George Washington that nations were to interpret treaty obligations for themselves but that "the tribunal of our consciences remains, and that also of the opinion of the world." He added that "as we respect these, we must see that in judging ourselves we have honestly done the part of impartial and rigorous judges."

To date in the war on terrorism, including the victims of the Sept. 11 attacks and all U.S. military personnel killed in action in Afghanistan and Iraq, America's losses total about 2 percent of the forces we lost in World War II and less than 7 percent of those killed in Vietnam. Yet we did not find it necessary to compromise our honor or abandon our commitment to the rule of law to defeat Nazi Germany or imperial Japan, or to resist communist aggression in Indochina. On the contrary, in Vietnam — where we both proudly served twice — America voluntarily extended the protections of the full Geneva Convention on prisoners of war to Viet Cong guerrillas who, like al-Qaida, did not even arguably qualify for such protections.

The Geneva Conventions provide important protections to our own military forces when we send them into harm's way. Our troops deserve those protections, and we betray their interests when we gratuitously "interpret" key provisions of the conventions in a manner likely to undermine their effectiveness. Policymakers should also keep in mind that violations of Common Article 3 are "war crimes" for which everyone involved — potentially up to and including the president of the United States — may be tried in any of the other 193 countries that are parties to the conventions.

In a letter to President James Madison in March 1809, Jefferson observed: "It has a great effect on the opinion of our people and the world to have the moral right on our side." Our leaders must never lose sight of that wisdom.

Retired Gen. P. X. Kelley served as commandant of the Marine Corps from 1983 to 1987. Robert F. Turner is co-founder of the University of Virginia's Center for National Security Law and a former chair of the American Bar Association's Standing Committee on Law and National Security. They wrote this commentary for The Washington Post.