A secret Justice Department memo detailing in great length when the president has the authority to unilaterally order American citizens murdered without so much as a criminal charge has been released.

The 16-page white paper titled "Lawfulness of a Lethal Operation Directed Against a U.S. Citizen Who is a Senior Operational Leader of Al-Qaida or An Associate Force" was leaked to NBC's Michael Isikoff, who notes that people deemed to be in those categories could be killed "even if there is no intelligence indicating they are engaged in an active plot to attack the U.S" and that it was used to justify "the September 2011 strike in Yemen that killed alleged al-Qaida operatives Anwar al-Awlaki and Samir Khan. Both were U.S. citizens who had never been indicted by the U.S. government nor charged with any crimes. "

We've know for months that the DOJ had offered up a legal justification allowing such extra-judicial killings and that the rationale was constructed to give maximum latitude to the president. There is, in that sense, not much new here. But the matter-of-fact and detailed legalese contained in the memo is nonetheless chilling.

Indeed, the first paragraph of the white paper specifically notes, "The paper does not attempt to determine the minimum requirements necessary to render such an operation lawful; nor does it assess what might be required to render a lethal operation against a U.S. citizen lawful in other circumstances." Instead, it devotes its 16 pages to the narrow case of "the circumstances in which the U.S. government could use lethal force in a foreign country outside the areas of active hostilities against a U.S. citizen who is a senior operational leader of al-Qa'ida or an associated force."

Under that narrow case, the paper concludes, three conditions must be met: "(1) an informed, high-level official of the U.S. government has determined that the targeted individual poses an imminent threat of violent attack against the United States; (2) capture is infeasible, and the United States continues to monitor whether capture becomes feasible and (3) the operation would be conducted in a manner consistent with applicable law of war principles."

The rest of the paper goes at great lengths to construe these three conditions so broadly as to render them practically meaningless, thus giving maximum flexibility to the will of the president.

Note that the conditions omit reference to the United States Constitution, due process, warrants, criminal charges, judicial oversight, or consultation with the legislature. This, despite the fact that the paper is only considering the very narrow case of U.S. citizens who are not engaged in direct combat with U.S. forces.

Indeed, the memo only grants that U.S. citizens "may have rights under the Due Process Clause and the Fourth Amendment [emphasis mine]" and argues that the right not to be murdered by one's own government "must be balanced against the United States' interest in forestalling the threat of violence and death to other Americans." That much, of course, is true: even in domestic law, police have the authority to use lethal force to protect against imminent harm to innocents; yesterday's FBI raid against Alabama kidnapper Jimmy Lee Dykes is a case in point.

But the DOJ here defines "imminent harm" in a way that would never stand in a domestic criminal case, including anyone who is merely "actively engaged in planning operations to kill Americans." Further, page 7 of the memo defines the imminence out of "imminent threat," declaring, it "does not require the United States to have clear evidence that a specific attack on U.S. persons and interests will take place in the immediate future." Why? Citing the 9/11 attacks, they reason that requiring "the United States to refrain from action until preparations for an attack are concluded, would not allow the United States sufficient time to defend itself."

If a group in, say, Chicago was suspected of planning a terrorist operation against Americans, no one would claim that the president could authorize a drone strike on the compound. To be sure, part of the reason is that condition (2) wouldn't exist; we have the ability to attempt capture and arrest in domestic situations. But that's not the whole or even the main reason; we simply don't allow police to kill other than to prevent imminent bodily harm to themselves or the public. The mere planning of a future killing—even a mass killing—would not qualify.

Additionally, while targeting a specific person for killing sounds an awful like an assassination, the paper assures us otherwise, reasoning that " In the Department's view, a lethal operation conducted against a U.S. citizen whose conduct poses an imminent threat of violent attack against the United States would be a legitimate act of national self-defense that would not violate the assassination ban."

Because those being targeted pursuant to this memo are members of or associated with al Qaeda, the paper reasons, they're subject to the law of war, not U.S. domestic law. They cite several cases, including the 2004 Hamdi decision, that note that U.S. citizens who join an enemy force may be targeted in the same manner as non-citizen members of that force during wartime.

That's a rather uncontroversial position with respect to a uniformed military force; it's a murky position, indeed, applied to a criminal organization operating outside the law of war. As a December report from Human Rights First notes, "Targeted killing is lawful in an armed conflict pursuant to the rules of international humanitarian law, also known as the law of armed conflict (IHL/LOAC), which permit lethal targeting of members of enemy armed forces and others while they directly participate in hostilities." It's doubtful whether al Qaeda, much less the undefined "associated groups," qualifies under that definition.

National Journal's Ron Fournier argues that, "If killing Americans with no due process is OK when their alleged crime is consorting with al-Qaida, it's not a huge intellectual leap to give government officials the same judge-and-jury authority over other heinous acts such as mass murder, drug trafficking, and child pornography." That overstates the case. Despite the use of the "war on" rhetoric to describe our policies against domestic criminal conduct, nobody suggests a state of war exists with domestic criminal groups. Further, the fact that people engaging in those activities can feasibly be captured and given due process would rule them out for extra-judicial killings even under the broad mandate of the DOJ white paper.

There's no denying that al Qaeda poses a unique threat to the safety of American citizens. Operating in ungoverned spaces of Pakistan, Yemen, and elsewhere, they're largely out of the reach of traditional law enforcement. If al-Awlaki or Khan were performing the exact same acts in Cleveland—or, indeed, London, Paris, or Sydney—they would have been targeted for arrest and extradition, not assassination.

Even so, American citizens should nonetheless be wary of granting the president the power to single out citizens for killing based simply on his own judgment. Aside from being plainly unconstitutional, it's simply too much trust to place in a single individual. At the very least, the rules ought to be spelled out in legislation that has passed both Houses of Congress and survived judicial scrutiny for constitutionality rather than made internally.

Further, in addition to checks and balances, there has to be more transparency. The notion that the government can compile a list of citizens for killing, not tell anyone who's on it or how they got there, is simply un–American. Surely, a modern version of a WANTED: DEAD OR ALIVE notice could be publicly circulated, with a listing of the particulars. Maybe the named individual would turn himself in rather than wait for the drones to find him. Or maybe he'd hire an attorney to present evidence he's not actually an imminent threat to American citizens.

For centuries, civilized societies have understood that even wars must be fought according to rules, which have developed over time in response to changing realities. Rules are even more important in endless, murky wars such as the fight against Islamist terror groups. Currently, we're letting whomever is in the Oval Office pick and choose from among the existing rules, applying and redefining them based on his own judgment and that of his advisors. We can do better.

James Joyner is managing editor of the Atlantic Council.