If you really want Washington’s chattering classes to pay attention to something, an old saying goes, leak it to the media.

Whoever leaked the Justice Department’s 16-page confidential “white paper” memo on the use of armed drones to NBC News sparked a long-overdue debate about something that makes both political sides feel uneasy: targeted killings by drone -- especially when the targets are American citizens.

Drones aren’t the problem. As tools of war they’re a lot less likely than traditional bombing to kill innocent civilians. They avoid the hazards of putting American boots on the ground. As retired Marine Gen. Stephen A. Cheney, who heads a defense-oriented think tank, put it, “Any time you can use a drone instead of using a Marine, I think it’s a good thing.”

Most other Americans love drones, too, judging by the polls. An overwhelming 83 percent in a Feb. 8 Washington Post poll approved of Obama’s drone strikes overseas. But support fell to a less-robust 65 percent if the terror suspects are American citizens living abroad.

Targeting our fellow Americans has been a very real issue since September 2011, when a drone strike in Yemen killed Anwar al-Awlaki and Samir Khan, two al-Qaida operatives and U.S. citizens. Another strike two weeks later killed six others, including Awlaki’s 16-year-old son, Abdulrahman, another American.

Although none had been formally charged with any crimes by the U.S. government, it’s pretty clear that Awlaki had it coming. The American-born cleric was believed to be directly involved in the infamous “underwear bomber” plot, among others. With their English skills, intelligence experts say, he and Khan, an Internet publisher and propagandist, provided important inspirational voices to potential recruits in the West.

There probably would be fewer questions about their rights to due process if we were in a conventional declared war. But the post-Sept. 11 counterterror war often has found itself on shaky legal ground.

I objected when the Bush administration appeared to stretch reasonable legal and moral limits on torture, detentions, renditions and targeted killings -- and I object just as strenuously to President Barack Obama administration dancing around the seriousness of this issue. He’s a former constitutional law teacher. He should know better.

That debate has stirred up with a new fury after NBC’s Michael Isikoff revealed the white paper memo. It formally lays out criteria under which the U.S. government can kill Americans by drone who are “senior operational leaders” of al-Qaida or “an associated force” -- even when there is no intelligence indicating they are engaged in an active plot to attack the U.S.

We sort of knew that already. Atty. Gen. Eric Holder endorsed the constitutionality of targeted killings of Americans in a speech at Northwestern University Law School last March. He said such hits could be justified if government officials determine the target poses “an imminent threat of violent attack,” although he did not define how “imminent” the threat has to be.

Neither does the memo disclosed by NBC, which is undated.

And last May, White House counterterrorism advisor John Brennan also cited domestic law and the Constitution to justify drone strikes.

But the confidential white paper goes farther than Holder’s and Brennan’s statements. For example, it “does not require ... clear evidence that a specific attack ... will take place in the immediate future.”

Instead, it says, an “informed, high-level” official of our government may determine that the targeted American has been “recently” involved in “activities” that pose a threat, and capture is “infeasible” -- although the memo does not define “recently” or “activities.”

The white paper, in short, invites more questions than it answers. Congress in its oversight role needs to engage in a thorough debate over how drone strikes can be conducted without handcuffing our nation’s ability to strike quickly and effectively.

Senate Intelligence Committee Chairman Dianne Feinstein suggested a new layer of judicial oversight similar to the Foreign Intelligence Surveillance Court, which issues secret warrants for wiretaps.

If so, the authority should be granted broadly enough to respond to strike requests without waiting for court approval, yet narrowly enough to avoid taking out the Bill of Rights as collateral damage.