WASHINGTON -- Last fall, as they tracked a suspected Al Qaeda leader across the brown highlands of Yemen, CIA operatives also worked their way through a secret checklist: the rules for "targeted killing," the newest front in America's war on terrorism.
They had won the permission of Yemen's government for an airstrike.
They had identified their quarry, Qaed Sinan Harithi, believed to be one of the planners of the 2000 attack in Yemen on the U.S. Navy destroyer Cole.
They had learned that Harithi was about to drive across the country, offering them a chance at a clean shot without civilians nearby.
One more thing: They had learned -- apparently from a Yemeni agent on the ground -- that the men in Harithi's group had gotten into one car, the women into another.
"If the women hadn't gotten into another car, we wouldn't have fired," one official said later.
When Harithi's SUV was in open countryside, the order was given to fire. An unmanned Predator aircraft, launched from the nearby African nation of Djibouti and flown remotely by an operator on the ground, was already over Harithi's path. It launched a Hellfire missile that slammed into the SUV and killed six men, including Harithi. A seventh reportedly escaped.
The operation was virtually perfect, U.S. officials say: strategically successful and, they maintain, legal under international law.
Even though the CIA wasn't sure who else was in the car, the customary rules of armed conflict say that anyone sitting next to a legitimate target such as Harithi was, in effect, accepting the risk of imminent death.
"Having defined this as an act against a military adversary and applying the standards of international law, this was within the legal rights of a nation at war," said Sen. Bob Graham (D-Fla.), chairman of the Senate Intelligence Committee.
But the mission in Yemen was, in a sense, an easy case. When future targeted-killing missions occur -- and they almost surely will, officials say -- they are likely to pose more difficult questions.
"What do we do, next time, if the women get into the car?" asked another member of the Intelligence Committee.
* Are the CIA's rules of engagement the right ones?
* Are Americans ready to accept targeted-killing missions that aren't as "clean" as the one in Yemen -- for example, missions that kill clearly innocent civilians?
* And if the CIA kills more suspected terrorists in more countries, will it have the unintended effect of "legitimizing" terrorist attacks against U.S. military officers in foreign countries or even at home?
"I think what we are seeing is the emergence of a new interpretation of customary international law regarding assassination," said Gary Solis, who has taught military law at West Point and Georgetown University.
"Until just a few months ago, we would all have expressed abhorrence ... of targeting individuals off the battlefield," he said. "But now, having had it brought home to us, we are taking a new approach.
"There would be good reason to be cautious," Solis said. "International law evolves because we want reciprocity. As it is applied to others, so shall it be applied to us. Those guidelines are wise because the military realize that at some point, they're going to be subject to the same kind of treatment."
The targeted-killing campaign and the CIA's central role in running it were ordered by President Bush after the Sept. 11 attacks in a secret intelligence finding, a legal document authorizing a covert action.
Under the finding, the CIA has developed a list of Al Qaeda leaders known as "high-value targets" for their roles in past terrorist attacks and their likely planning of future strikes.
The existence of the finding and the target list was reported last year, although both are still officially secret. In the ensuing months, the CIA expanded the list and developed formal rules of engagement for its targeted-killing operations, according to U.S. civilian, intelligence and military officials who all requested anonymity.
They refused to provide details but said the rules are designed essentially to make sure that any covert killings comport with U.S. law and with the "customary rules of armed conflict" that are a recognized part of international law under the 1907 Hague Convention and the 1949 Geneva Convention.
An executive order first issued by President Ford in 1975 prohibits U.S. intelligence agencies from engaging in assassination. But several presidents -- including George Bush, the current president's father, and Bill Clinton -- have interpreted that rule as forbidding the slaying of civilian political leaders, not terrorist figures.
The distinction is not always easy. In October 2001, the Air Force sought permission to attack a convoy of Taliban vehicles in Afghanistan, but a Pentagon lawyer argued against the strike -- in part because women and children might be harmed but also because the Taliban leader, Mullah Mohammed Omar, might be considered a civilian. The attack was called off.
One reason the CIA is running the targeted-killing campaign, even though the Air Force owns most of the Predators, is that it was more enthusiastic about the idea of shooting individual enemy leaders, one official said.
But in the case of Al Qaeda, the Bush administration has defined all of the terrorist group's members as "enemy combatants," making them vulnerable to attack anywhere, at any time, under traditional international law.
Under the rules, CIA operatives must make every effort to identify their targets correctly, as they did in the case of Harithi in Yemen. Officials say they want to avoid killing innocent people because of mistaken identity. (An earlier strike on Harithi was called off at the last minute when a CIA analyst said he wasn't sure the agency had the right man, officials say.)
The CIA and U.S. military units are supposed to attempt to capture Al Qaeda suspects alive if possible -- not because that is required by international law (it isn't) but because the suspects might be useful sources of information. In the case of Harithi, however, an earlier attempt to capture him using Yemeni troops failed, leaving 18 Yemenis dead. As in regular warfare, the CIA is trying to carry out its operations without killing bystanders. In Yemen, "we exercised a lot of care to minimize collateral damage," an official said.
And, where possible, the U.S. is seeking the permission of local governments before carrying out targeted killings on foreign soil -- although officials suggest that Bush is willing to waive that rule if necessary. Launching a targeted killing in another country without its assent is normally a violation of international law, legal scholars say.
"There may be some cases where we can't make it conform to international law," one official said. "In that case, let's just make it conform to our law."
Such an operation would probably create a greater political backlash than did the Yemen strike, which prompted only modest protests abroad and almost none at home.
The CIA does not officially acknowledge the targeted-killing program, but it says it has devoted great care to designing guidelines for all covert actions.
"We have more lawyers than Predator pilots," one official said.
Still, members of the congressional oversight committees on intelligence say they worry about command-and-control issues.
"Predator gives you the ability to see a target and, in a matter of seconds, to hit it," Graham said. "Is it the right target? Are there innocent civilians nearby? All those decisions have to be made in a matter of seconds. You run the risk of being too cautious or, on the other end, too willing to pull the trigger.
"So far, as far as we know, the judgments have been good," he said.
Rep. Porter J. Goss (R-Fla.), chairman of the House Intelligence Committee, said he isn't sure the decision-making process is clear enough.
"That mechanism still needs to be set up," Goss said.
And the congressman raised a broader concern: Will increasing reliance on targeted killings prompt the CIA to take on additional paramilitary functions?
"There's going to be tension between when is it 'military' and when is it 'other,' " Goss said. "What are the new ground rules about using lethality [in] what we used to call covert action? How much capability will be thrown to nonmilitary agencies?
"I think there's still ambiguity," he said.
But as for the basic concept of targeting individual terrorists for elimination, there has been no apparent controversy.
"We set out to kill people in Afghanistan during the Clinton administration," Graham noted. "We just didn't have as sophisticated a system as Predator at the time."
During the 1990s, he recalled, the U.S. government tried to kill Osama bin Laden by firing missiles at his camps and by hiring local warlords to shoot him.
There is no indication that Bush's authorization of targeted killings restricts the CIA to long-distance weapons like the Predator and its Hellfire missiles. In other words, officials say, the CIA is legally free to send snipers into foreign cities to kill Al Qaeda leaders at close range.
"That line was crossed before," Graham said.
"When you're dead, you're dead," said a former military official who participated in the administration's internal discussions of targeted killings. "If the means of killing you is a .22-caliber bullet or a Hellfire missile, it makes no difference."
Charles Allen, deputy general counsel of the Defense Department, said U.S. actions against Al Qaeda in Yemen and elsewhere "have been consistent with the principles of the law of armed conflict."
"Our conflict is with Al Qaeda and with other international terrorists and their supporters," he said in an interview in December with the Crimes of War Project, an independent group that monitors military actions. "The world agrees that the U.S. was attacked and is in armed conflict with that stated enemy. Therefore, in exercising our right of self-defense, we can target members of that enemy force....
"When we have a lawful military target that the commander determines needs to be taken out, there is by no means a requirement under the law of armed conflict that we must send a warning to those people and say, 'You may surrender rather than be targeted.' "
Legal scholars say the administration's argument holds up, but only as long as the CIA sticks to a clear set of rules.
"What they did in Yemen looks legal.... But is there a slippery slope there that causes concerns? Yes," said Barry Kellman, a professor at DePaul University's International Human Rights Law Institute.
"In the administration's defense, the fact that they're devising well-thought-out rules of engagement is extraordinarily important," he said. "The law is not a straitjacket. The law is nuanced enough, for example, to recognize that police sometimes have to use deadly force to take down a dangerous criminal."
"The problem is, of course, Al Qaeda doesn't really fit into the traditional law of armed conflict, because it's not a state," noted Robert F. Turner, a professor at the University of Virginia's Center for National Security Law.
"In fact, the best analogy is piracy, and there is international law that deals with pirates," Turner said.
"They are 'the common enemies of mankind,' and as such they may be apprehended or attacked by anyone."
Times staff writers Esther Schrader and Greg Miller contributed to this report.