The memo makes many contested claims that will be analyzed by legal experts who are better able than I am to identify and explain potentially problematic precedents. On first read, I am nevertheless struck by how few words are spent defending extrajudicial killing against constitutional, as opposed to statutory, objections. After all, the Fifth Amendment is emphatic: "No person shall... be deprived of life, liberty, or property, without due process of law." Citing Hamdi v. Rumsfeld and Mathews v. Eldridge, the memo argues that the Fifth Amendment prohibition on killing without due process is subject to a "balancing test" that weighs the right not to be extrajudicially killed against the government's interests and whatever burdens it would face in extending due process.

That itself is a potentially dangerous precedent.

The memo continues: "We believe similar reasoning supports the constitutionality of the contemplated operations here. As explained above, on the facts represented to us, a decision-maker could reasonably decide that the threat posed by al-Aulaqi's activities to United States persons is 'continued' and 'imminent.'"

This passage is alarming for two reasons:

1) It asserts that the executive branch can kill Americans in secret under the standard, "a decision-maker could reasonably decide ..." Dick Cheney was "a decision-maker." So was J. Edgar Hoover. Are we prepared to accept that Fifth Amendment protections are null based on a relativistic standard as interpreted in secret by men like them?

2) The memo treats the representation that al-Awlaki posed an "imminent" threat as important. But unless it is hidden in a redaction, the memo does not address how "imminent" is defined, and there is good reason to believe that the Obama administration has defined it so dubiously as to render the term meaningless. I explored this problem at greater length back on February 5, 2013, when Michael Isikoff published another memo that dealt with extrajudicial killings. It set, as a precondition of such killings, "an imminent threat of violent attack."

That may seem reassuring. After all, there aren't that many circumstances when an attack is imminent. It would seem to severely constrain extrajudicial assassinations. But that memo reassures the reader with the rhetorically powerful word "imminent," only to define it down in a way that makes it largely meaningless—so much so that it's reminiscent of George W. Bush's misuse of "imminent" to characterize the threat posed by Iraq. What does it mean, for you personally, when you hear that someone poses "an imminent threat of violent attack against the United States"? Here's a passage where the Obama administration articulates what it means by imminent:

Certain aspects of this legal framework require additional explication. First, the condition that an operational leader present an "imminent" threat of violent attack against the United States does not require the United States to have clear evidence that a specific attack on U.S. persons will take place in the immediate future.

They've defined the term in a way that excludes its only actual meaning!