Can the president kill an American simply because the person is dangerous and his arrest would be impractical? Can the president be judge, jury and executioner of an American in a foreign country because he believes that would keep America safe? Can Congress authorize the president to do this?

Earlier this week, U.S. Attorney General Eric Holder attempted to justify presidential killing in a speech at Northwestern University law school. In it, he recognized the requirement of the Fifth Amendment for due process. He argued that the president may substitute the traditionally understood due process -- a public jury trial -- with the president's own novel version of it; that would be a secret deliberation about killing. Without mentioning the name of the American the president recently ordered killed, Holder suggested that the president's careful consideration of the case of New Mexico-born Anwar al-Awlaki constituted a substituted form of due process.

Holder argued that the act of reviewing al-Awlaki's alleged crimes, what he was doing in Yemen and the imminent danger he posed provided al-Awlaki with a substituted form of due process. He did not mention how this substitution applied to al-Awlaki's 16-year-old son and a family friend, who were also executed by CIA drones. And he did not address the utter absence of any support in the Constitution or Supreme Court case law for his novel theory.

The Fifth Amendment to the Constitution states that the government may not take the life, liberty or property of any person without due process. Due process has numerous components, too numerous to address here, but the essence of it is "substantive fairness" and a "settled fair procedure." Under due process, when the government wants your life, liberty or property, the government must show that it is entitled to what it seeks by articulating the law it says you have violated and then proving its case in public to a neutral jury. And you may enjoy all the constitutional protections to defend yourself. Without the requirement of due process, nothing would prevent the government from taking anything it coveted or killing anyone -- American or foreign -- it hated or feared.

The killing of al-Awlaki and the others was without any due process whatsoever, and that should terrify all Americans. The federal government has not claimed the lawful power to kill Americans without due process since the Civil War; even then, the power to kill was claimed only in actual combat. Al-Awlaki and his son were killed while they were driving in a car in the desert. The Supreme Court has consistently ruled that the Constitution applies in war and in peace. Even the Nazi soldiers and sailors who were arrested in Amagansett, N.Y., and in Ponte Vedra Beach, Fla., during World War II were entitled to a trial.

The legal authority in which Holder claimed to find support was the Authorization for the Use of Military Force (AUMF), which was enacted by Congress in the days following 9/11. That statute permits the president to use force to repel those who planned and plotted 9/11 and who continue to plan and plot the use of terror tactics to assault the United States. Holder argued in his speech that arresting al-Awlaki -- who has never been indicted or otherwise charged with a crime but who is believed to have encouraged terrorist attacks in the U.S. -- would have been impractical, that killing him was the only option available to prevent him from committing more harm, and that Congress must have contemplated that when it enacted the AUMF.

Even if Holder is correct -- that Congress contemplated presidential killing of Americans without due process when it enacted the AUMF -- such a delegation of power is not Congress' to give. Congress is governed by the same Constitution that restrains the president. It can no more authorize the president to avoid due process than it can authorize him to extend his term in office beyond four years.

Instead of presenting evidence of al-Awlaki's alleged crimes to a grand jury and seeking an indictment and an arrest and a trial, the president presented the evidence to a small group of unnamed advisers, and then he secretly decided that al-Awlaki was such an imminent threat to America 10,000 miles away that he had to be killed. This is logic more worthy of Joseph Stalin than Thomas Jefferson. It effectively says that the president is above the Constitution and the rule of law, and that he can reject his oath to uphold both.

If the president can kill an American in Yemen, can he do so in Peoria? Even the British king, from whose tyrannical grasp the American colonists seceded, did not claim such powers. And we fought a Revolution against him.