For the last several years, the White House has had what it calls a "disposition matrix" — a methodical, legally vetted procedure for tracking and capturing or killing suspected terrorists.
Much more than a mere kill list, the disposition matrix, first revealed last fall in a series of Washington Post articles, is a process whereby each suspect is profiled, located, tracked and monitored.
Every three months, the Central Intelligence Agency and the National Counterterrorism Center review the matrix and draw up lists of which suspected terrorists should be killed, by drone strike or by some other method.
The president has final approval on each targeted killing, which is usually carried out by CIA drones remotely operated from American military bases around the world.
Because targeted killings are considered a military operation within the scope of war, suspects are not notified, charged or tried before being targeted.
The practice of targeted killings has been under fire since the Bush administration began them, but criticism ramped up as the Obama administration greatly expanded the program.
In late 2011, a line was crossed — three Americans associated with al-Qaida were killed by counterterrorism drone strikes in Yemen, including a 16-year-old boy who was not a target.
Here's how the disposition matrix works — and how it could be applied to terrorism suspects on American soil.
Popping up on the grid
According to anonymous sources both within and outside the Obama administration, it takes several steps to get on the disposition matrix.
First come data from various agencies, such as the CIA, the National Security Agency or the military's Joint Special Operations Command. The agencies flag individuals as potentially belonging to terrorist groups or possibly otherwise involved in terrorist activity.
That group of names goes to the National Counterterrorism Center, or NCTC, part of the Office of the Director of National Intelligence. The NCTC culls the list for people who are, in the estimation of intelligence analysts, plotting attacks against Americans.
At that point, the list goes to a commission chaired by the White House counterterrorism adviser, currently Lisa Monaco. The commission is made up of senior officials from the intelligence agencies and the military, the State Department and the FBI.
The list of names is narrowed and then sent to the president, who has the final say on whether each individual lives or dies. One of the deciding criteria is, according to the Obama administration, whether a targeted person poses an imminent threat to the United States.
Although most targeted killings have taken place in recognized combat zones, such as Afghanistan, Somalia, Yemen and Pakistan, the disposition matrix also applies to people outside of those zones.
Just a smokescreen?
Bill Roggio, managing editor of the Long War Journal, an online news site published by the Washington, D.C.-based Foundation for Defense of Democracies, doesn't believe that such a "disposition matrix" really exists — at least not in the way the administration presents it — because many of the targets are local nuisances rather than global threats.
In March 2012, for example, a U.S. drone hit an al-Qaida weapons cache in Yemen and killed some local al-Qaida leaders.
The week before, fighters from al-Qaida in the Arabian Peninsula had defeated a Yemeni army unit.
While that defeat was certainly a big concern for the Yemeni government and military, there's no evidence any of the al-Qaida leaders killed in the subsequent drone strike were planning an attack on the United States.
"You can't tell me that these guys were an imminent threat," Roggio said.
Roggio sees the drone strikes — and by extension other targeted killings — as a sign that there is no overarching strategy being applied.
"It's a tactical move, not a strategic one," he said.
Bringing the war back home
The question for civil libertarians is whether targeted killings or the disposition matrix could ever be used against people inside the United States.
Unfortunately, answering that is more complicated that it sounds.
"The problem is that, although the president and the attorney general have stated that the government would not conduct a drone strike on U.S. soil absent 'extraordinary circumstances,' the government's publicly known interpretation of its legal authority to conduct strikes does not contain any geographic restriction at all," said Brett Max Kaufman, a national security fellow at the American Civil Liberties Union.
Kaufman referred to a letter sent on March 4 from Attorney General Eric Holder to Sen. Rand Paul (R-Ky.) during hearings for then-White House counterterrorism adviser John O. Brennan, who had been nominated, and was later confirmed, as CIA director.
Holder said that although the United States had "no intention" of carrying out drone strikes on U.S. soil, he could imagine a situation such action might be "necessary and appropriate," such as during attacks as catastrophic as Pearl Harbor or 9/11.
Three days later, Holder sent a second letter to Paul, answering Paul's question: "Does the President have the authority to use a weaponized drone to kill an American not engaged in combat on American soil?"
"The answer to that question is no," Holder wrote.
The American Civil Liberties Union and the Center for Constitutional Rights are currently suing the U.S. government on behalf of Nasser al-Aulaqi, father of al-Qaida in the Arabian Peninsula leader Anwar Al-Awlaki, one of the three Americans killed in by drone strikes in Yemen in the fall of 2011.
For the ACLU, the problem is that without any judicial oversight, the government is essentially deciding on an execution. The suit charges that Al-Awlaki's constitutional rights were violated because there was no due process — no indictment was filed against him.
In May 2012, Holder admitted in a letter to Senate Judiciary Committee Chair Patrick Leahy (D- Vt.) that the United States had killed Al-Awlaki, who was born in New Mexico, attended college in Colorado and became a prominent imam in Washington, D.C.
Al-Awlaki's 16-year-old son, Colorado-born Abdulrahman Al-Awlaki, was killed in a separate drone strike in Yemen two weeks later. He was not a target, but was accompanying al-Qaida members who were.
A third American citizen, Samir Khan, who was born in Saudi Arabia of Pakistani parents but grew up in New York, was killed in the same attack that killed Al-Awlaki.
Khan, who edited and published the al-Qaida English-language online magazine Inspire (alleged to be the source of the "pressure cooker bomb" plans used by the Boston Marathon bombers ), was not a target, but had been accompanying Al-Awlaki, who was.
Opening arguments in the ACLU lawsuit — which may reveal more information about drone strikes and targeted killings — are scheduled for July 19.
So could it happen?
Except within the boundaries laid down by the Foreign Intelligence Surveillance Act of 1978, the CIA and NSA have no authority to act within the borders of the United States.
(The recently revealed court order authorizing the NSA to collect Verizon phone logs was issued by the FISA court on behalf of the FBI, and the NSA's PRISM Internet-traffic-monitoring system is theoretically directed only at non-U.S. persons.)
The last time anything close to a government bombing took place in the United States was in 1985, when Philadelphia police used a helicopter to drop bombs on a fortified house occupied by members of the radical black-nationalist group MOVE during an armed standoff.
Eleven people died in the resulting fire, including five children, and 65 homes were destroyed in the neighborhood. In 1996, the city of Philadelphia paid $1.5 million to siege survivors and relatives.
The outcry over two federal law-enforcement paramilitary actions — at Ruby Ridge, Idaho, in 1992 and at the Branch Davidian compound outside Waco, Texas, in 1993 —would also give any politician pause before ordering a full-on military assault on American soil.
But that's not to say it could never happen. Holder left open the possibility of a Pearl Harbor-style attack in his letter to Paul.
The man Holder was supporting — current CIA director Brennan, said by experts to be the architect of the disposition matrix and head of the agency tasked with carrying out drone strikes — was even more expansive.
In written answers to questions posed by the Senate Intelligence Committee, Brennan said there was no "geographical limitation" to the scope of targeted killings.
"On your question about whether I would support legislation to authorize the use of force outside of 'hot' battlefields," Brennan wrote, "I believe we currently have the authority to take action against al-Qaida and associated forces."
"The 2001 Authorization for the Use of Military Force does not contain a geographical limitation," Brennan added. "Consequently, I do not believe additional legislation along these lines is necessary."