The strike, launched from a Predator unmanned aerial vehicle, killed Qaed Salim Sinan al-Harethi, said to be al Qaida's top man in Yemen and one of the architects of the October 2000 suicide bombing of the USS Cole that killed 17 sailors.
Al-Harethi is not the first al Qaida member the United States has personally targeted, but he is the first the government has killed outside the borders of Afghanistan.
The White House, CIA and Pentagon have been very close-lipped about the operation, other than Deputy Defense Secretary Paul Wolfowitz' acknowledgement of its success to CNN in an interview this week.
But Sunday's incident does not seem to meet the "assassination test," according to experts.
"Based on what has been reported in the press, this is viewed as a military action against enemy combatants which would take it out of a realm of assassination," said Suzanne Spalding, a former deputy general counsel with the CIA and now an official with the American Bar Association. "It does seem to me this was characterized as a military operation in the war on terrorism -- not a rhetorical war -- and that these are enemy combatants. You shoot to kill enemy combatants."
An executive order from President Ford, subsequently upheld and strengthened by both Jimmy Carter and Ronald Reagan, barred the United States from engaging in assassination. Ford's order was a reaction to multiple failed and embarrassing attempts by the CIA to have foreign leaders assassinated, including several attempts on Cuba's Fidel Castro.
Steve Aftergood, with the Federation of American Scientists' Project on Government Secrecy, agrees the strike was not a violation of the executive order.
"I thought that the Yemen strike was necessary and appropriate. These are people after all who declared war on us and defending ourselves is the right thing to do. The bottom line is these are bad people that need to be stopped, so the mission counts as a success," Aftergood told United Press International.
What makes the killing of an individual by the U.S. government rise to the level of assassination is that it is undertaken for political purposes during peace time, according to Duke University law professor Scott Silliman. The United States, he points out, is most emphatically at war.
Moreover, President Bush signed a finding allowing "lethal covert action" to be taken against al Qaida leader Osama bin Laden and his operatives last fall. The finding instructs the CIA to attack bin Laden's communications and security apparatus, as well as the entire infrastructure of the al Qaida network. For the first time since the ban on assassination went into effect, a lethal covert action finding specifically authorizes the targeting of an individual.
It came a few weeks after Congress passed a joint resolution authorizing the president to use "all necessary and appropriate force" against "persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001." Al Qaida, individual members and collectively, then, is firmly in the cross hairs.
But the incident nevertheless causes concern for Aftergood, Spalding and others who worry that the Bush administration's rules for this sort of covert action are intentionally vague and set a dangerous precedent for both the United States and other countries to follow.
"It is difficult to distinguish what we did in Yemen from what Israel has done with the Palestinians with targeted killings," Silliman told UPI.
As recently as July, White House spokesman Ari Fleischer criticized Israel for launching a "heavy handed" attack that killed Salah Shehadeh, the top commander of Hamas' military wing, Izzadine el-Qassa, in Gaza.
The attack by an F-16 with a single 2,000-lb bomb destroyed four buildings killing 14 others, including nine children, and wounding as many as 100, Palestinian authorities said at the time.
Fleischer's comment -- "this heavy-handed action does not contribute to peace" -- may have been a statement on the size of the bomb dropped and not the intent of the attack -- to kill a known terrorist.
Sunday's operation may erode the influence the United States has over Israel and other states that have been dealing with internal and external terrorist threats to their territory. Broadly interpreted, it could also be applied by other states to justify their own preemptive attacks on perceived adversaries.
"We are basically opening up and crafting a new tool and tactic which is not for (the United States) alone to use," Silliman said. "The United States is not the only one that can do this. We may be putting our own leadership at risk."
Sweden's Foreign Minister Anna Lindh warned of just such an outcome in comments this week about the Yemen operation. "Even terrorists must be treated according to international law. Otherwise, any country can start executing those whom they consider terrorists," she said.
The Bush administration, in its blanket refusal to discuss the details of the operation, has not answered why al-Hareth and the others were killed rather than tracked and arrested for interrogation.
Silliman says the new power that the United States has now wielded outside the confines of the Afghan battlefield has a simple justification: In the global war on terrorism the United States has a legitimate right to defend itself. But where can it take action and under what circumstances?
Defense Secretary Donald Rumsfeld has been very clear about the military's plan to take the war to the terrorists, wherever they are. He has said al Qaida has a presence in at least 60 nations, including the United States.
"If we do this outside the traditional combat area of Afghanistan, in Yemen -- could we not do it in Germany, Ottawa, or even in Cincinnati?" Silliman asked. "If you move outside a combat area to a non-combat area, then wherever al Qaida is becomes a legitimate target. The question is, do we (the United States) become the arbiter on whether a country is capable of dealing with the terrorists on their own?"
Aftergood shares the concern.
"It is a problematic precedent for the future because we really don't know what its implications are, we need greater clarity about the rules of the road not only for ourselves but for other countries. Others should not think or imagine we are willing to invade their territory and strike within their borders unannounced. That's not what we do, not what we stand for. National sovereignty is a value we uphold and respect," Aftergood said. "The fundamental value at stake here is the rule of law, including the laws of war."
What is needed is a more precise definition by the Bush administration of this new strategy.
"From a policy perspective we need to hear something that gives us a sense it is not arbitrary and completely open ended. That will make it a lot easier to accept the kinds of things that need to be done," Spalding told UPI.
"This is an area in which the application of laws of armed conflict is very difficult. We have a lot of experience employing laws of armed conflict -- what constitutes a military target, the appropriate use of force. This is anything but a traditional war. Applying those laws to specific targets in this situation is very tricky," warned Spalding. "We're sort of making it up as we go along because we are applying laws written for a very different context from ... today's environment."