WASHINGTON -- In my New York Times best-seller "Heroes Proved," the president of the United States orders the execution of an American citizen in the United States by using precision munitions fired from a remotely piloted aircraft, or RPA -- incorrectly referred to by our media as a drone. When the book came out last year, some critics derided the idea of a U.S. president's issuing an executive order to kill Americans in our homeland as "over the top" and "unthinkable." One even said the idea was "unfathomable." But thanks to Sen. Rand Paul, R-Ky., we now know the Obama administration already has contemplated such action. That ought to be troubling to every one of us.

On March 6, Paul took to the floor of the U.S. Senate in a 13-hour effort to block the confirmation of John Brennan as CIA director until the administration handed over its "legal, procedural and constitutional justification" for such "extrajudicial executions." The filibuster failed, and the Senate confirmed Brennan the following day. But the issues of constitutional protections for American citizens and the limits of executive power aren't going away. Nor should they.

This isn't about whether it's proper to kill enemy combatants on the battlefield. I have a citation for leading my Marines in "the execution of more than seventy day and night ambushes," during which scores of enemy soldiers were killed and sometimes captured -- without warning. Using Hellfire missiles or other "precision munitions" fired from Predator or Reaper RPAs on the battlefield is simply a long-distance ambush -- a safer means of killing our nation's enemies and a way to never have to take a prisoner.

In 1968-69, our targets in northern South Vietnam were all armed invaders. There was no doubt they posed an imminent threat to our safety and that of our comrades. That's not the case with the Obama administration's so-called drone program. Now the targets include American citizens overseas. That raises the very troubling prospect that key phrases in the Fifth Amendment no longer have meaning:

"No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury ... nor shall any person ... be deprived of life, liberty, or property, without due process of law."

Anonymous administration insiders claim that the president personally approves every name on the White House kill list. According to the tortured language of an undated 16-page Justice Department white paper that was leaked, "it would be lawful for the United States to conduct a lethal operation outside the United States against a U.S. citizen who is a senior, operational leader of al-Qa'ida or an associated force of al-Qa'ida without violating the Constitution."

The legal opinion, apparently drafted at the Department of Justice and the Obama White House without consultation with Congress, elaborates at length about how such lethal action against American citizens overseas does not violate any laws, treaties or international conventions or even Executive Order 12333, which bars assassination.

Most troubling, the white paper reduces due process to a determination made by "an informed, high-level official of the U.S. government ... that the targeted individual poses an imminent threat of violent attack against the United States." Though the document lists other restrictions -- e.g., capture must be infeasible -- and purports to limit "lethal operations" against American citizens to those involved with al-Qaida "in a foreign country," it does not define "imminent threat" and is silent about killing citizens here at home. In short, it raises more questions than it answers.

What about American citizens, overseas or here, believed to be affiliated with other threatening organizations besides al-Qaida -- such as Hamas, Hezbollah, the Muslim Brotherhood and Islamic Jihad? Who decides whether capture is feasible or not? Do we really want to establish a precedent that an American president or any "informed, high-level official of the U.S. government" can serve as chief prosecutor, judge, jury and executioner for American citizens? If so, who will hold him or her accountable?

When the matter came up at the White House press briefing March 7, Obama spokesman Jay Carney said, "The president has not and would not use drone strikes against American citizens on American soil." That's reassuring.

In a surreal twist, the Obama "drone program" was Washington's topic du jour as North Korean dictator Kim Jong Un's brutal regime announced, "Now that the U.S. is set to light a fuse for a nuclear war, the armed forces of the (Democratic People's Republic of Korea) will exercise the right to a pre-emptive nuclear attack."

That sounds as if it might even be an "imminent threat of violent attack against the United States." But unlike an American citizen in Pakistan, Yemen or Virginia, Kim doesn't have to worry about a missile fired from a drone over Pyongyang. That's forbidden by Executive Order 12333.

Carney says, "The United States is fully capable of defending against any North Korean ballistic missile attack." That's reassuring, too.

Oliver North is the host of "War Stories" on Fox News Channel and the author of the New York Times best-seller "Heroes Proved." To find out more about Oliver North and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate Web page at www.creators.com.

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