On September 30, 2011, in a northern province of Yemen, Anwar al-Awlaki, an American citizen and a senior figure in Al Qaeda in the Arabian Peninsula, finished his breakfast and walked with several companions to vehicles parked nearby. Before he could drive away, a missile fired from a drone operated by the Central Intelligence Agency struck the group and killed Awlaki, as well as a second American citizen, of Pakistani origin, whom the drone operators did not realize was present.

President Barack Obama had personally authorized the killing. “I want Awlaki,” he is said to have told his advisers at one point. “Don’t let up on him.” The President’s bracing words about a fellow American are reported in “Kill or Capture,” a recent and important book on the Obama Administration’s detention and targeted-killing programs, by Daniel Klaidman, a former deputy editor of Newsweek.

With those words attributed to Obama, Klaidman has reported what would appear to be the first instance in American history of a sitting President speaking of his intent to kill a particular U.S. citizen without that citizen having been charged formally with a crime or convicted at trial.

The due-process clause of the Fifth Amendment prohibits “any person” from being deprived of “life, liberty, or property without due process of law.” Obama authorized the termination of Awlaki’s life after he concluded that the boastful, mass-murder-plotting cleric had, in effect, forfeited constitutional protection by waging war against the United States and actively planning to kill Americans. Obama also believed that the Administration’s secret process establishing Awlaki’s guilt provided adequate safeguards against mistake or abuse—all in all, enough “due process of law” to take his life.

Awlaki was certainly a murderous character; his YouTube videos alone would likely convict him at a jury trial. Yet the case of Awlaki’s killing by drone strike is to the due-process clause what the proposed march of neo-Nazis through a community that included many Holocaust survivors in Skokie, Illinois, was to the First Amendment when that case arose, in 1977. It is an instance where the most onerous facts imaginable should lead to the durable affirmation of constitutional principle, as Skokie did. Instead, President Obama and his advisers have opened the door to violent action against American citizens by future Presidents when the facts may be much less compelling.

Last March, Eric Holder, the Attorney General, delivered an address at Northwestern University in which he sought to explain and justify the Awlaki killing, without ever naming the victim, apparently because such honesty would violate the Administration’s classification rules. Holder’s arguments are worth absorbing at length. He explained,

Now, it is an unfortunate but undeniable fact that some of the threats we face come from a small number of United States citizens who have decided to commit violent attacks against their own country from abroad. Based on generations-old legal principles and Supreme Court decisions handed down during World War II, as well as during this current conflict, it’s clear that United States citizenship alone does not make such individuals immune from being targeted. But it does mean that the government must take into account all relevant constitutional considerations with respect to United States citizens—even those who are leading efforts to kill innocent Americans…. An individual’s interest in making sure that the government does not target him erroneously could not be more significant. Yet it is imperative for the government to counter threats posed by senior operational leaders of al Qaeda, and to protect the innocent people whose lives could be lost in their attacks…. Let me be clear: an operation using lethal force in a foreign country, targeted against a U.S. citizen who is a senior operational leader of al Qaeda or associated forces, and who is actively engaged in planning to kill Americans, would be lawful at least in the following circumstances: First, the U.S. government has determined, after a thorough and careful review, that the individual poses an imminent threat of violent attack against the United States; second, capture is not feasible; and third, the operation would be conducted in a manner consistent with applicable law of war principles.

It would be difficult to list all of the ways in which Holder’s arguments are disturbing. Overall, the large-scale targeted killing of non-Americans affiliated with Al Qaeda during the Obama Administration’s first term raises many questions about legality and transparency. The more recent addition of Klaidman’s reporting, however, calls attention to one area, infrequently discussed, where it seems clear that the Obama Administration has driven right through a constitutional stop sign. This involves the second of Holder’s three conditions for killing a U.S. citizen who has joined Al Qaeda and is actively planning to kill Americans—that is, “capture is not feasible.”