Attorney General Eric Holder’s discussion of lethal force against U.S. citizens did not mention any individual by name, but his address followed the September killing of Anwar al-Awlaki, a senior figure in al-Qaeda’s Yemeni affiliate. (J. Scott Applewhite/AP)

The U.S. government has the right to order the killing of American citizens overseas if they are senior al-Qaeda leaders who pose an imminent terrorist threat and cannot reasonably be captured, Attorney General Eric H. Holder Jr. said Monday.

“Any decision to use lethal force against a United States citizen — even one intent on murdering Americans and who has become an operational leader of al-Qaeda in a foreign land — is among the gravest that government leaders can face,” Holder said in a speech at Northwestern University’s law school in Chicago. “The American people can be — and deserve to be — assured that actions taken in their defense are consistent with their values and their laws.”

Holder’s discussion of lethal force against U.S. citizens did not mention any individual by name, but his address was clearly animated by the targeting of Anwar al-Awlaki, a senior figure in al-Qaeda’s Yemeni affiliate. Awlaki, who was born in New Mexico, was killed in a U.S. drone strike in Yemen in September.

Since that operation, the Obama administration has faced calls to explain the legal framework behind its decision to target Awlaki and to release at least portions of a classified memorandum by the Justice Department’s Office of Legal Counsel that contains its evidence, reasoning and conclusions.

Holder’s speech represented the administration’s most elaborate public explanation to date for targeted killings. And it followed a prolonged internal debate about how to inform the public about one of the most extraordinary decisions a government can take without explicitly acknowledging the ongoing classified drone program.

Among the most revealing parts of the speech was Holder’s discussion of some of the factors the administration reviews before deciding that an individual represents an “imminent threat.” He said the critical factors include the “relevant window of opportunity to act, the possible harm that missing the window would cause to civilians and the likelihood of heading off future disastrous attacks against the United States.”

He said the president is not required by the Constitution to delay action until some “theoretical end stage of planning — when the precise time, place and manner of an attack become clear.”

The attorney general’s “flexible definition of ‘imminent threat’ is absolutely appropriate as applied to terrorist planners, but it may be unsettling to many in the international community who criticized President Bush for his principle of preemption,” said John B. Bellinger, who served as a legal adviser to the State Department in the George W. Bush administration.

Bellinger said he agreed with the attorney general’s statement of U.S. law for targeting an American, although he noted that the speech was less clear about how targeted killings comply with international legal rules.

There are no known U.S. citizens on target lists maintained by the CIA or the military’s Joint Special Operations Command.

Holder emphasized Monday that he would discuss the issue only in the abstract and would not “discuss or confirm any particular program or operation.”

“In the deliberations over whether the attorney general should make a speech, the CIA was an early and vocal proponent of explaining publicly the legal framework for the use of force in U.S. counterterrorism operations,” said a U.S. official familiar with the interagency deliberations and the drafting of the speech.

Critics of the administration said the government has assumed dangerous new powers.

“While the speech is a gesture towards additional transparency, it is ultimately a defense of the government’s chillingly broad claimed authority to conduct targeted killings of civilians, including American citizens, far from any battlefield without judicial review or public scrutiny,” said Hina Shamsi, director of the ACLU’s National Security Project.

Holder argued that a careful and thorough executive branch review of the facts in a case amounts to “due process” and that the Constitution’s Fifth Amendment protection against depriving a citizen of his or her life without due process of law does not mandate a “judicial process.”

“Where national security operations are at stake, due process takes into account the realities of combat,” Holder said. “Some have argued that the president is required to get permission from a federal court before taking action against a United States citizen who is a senior operational leader of al-Qaeda or associated forces. This is simply not accurate.”

Holder said that the question of “whether the capture of a U.S.-citizen terrorist is feasible is a fact-specific, and potentially time-sensitive, question.”

“Given the nature of how terrorists act and where they tend to hide,” he continued, “it may not always be feasible to capture a United States-citizen terrorist who presents an imminent threat of violent attack. In that case, our government has the clear authority to defend the United States with lethal force.”

Holder also noted that in using lethal force, the United States must make sure that it is acting within the laws of war by ensuring that any target is participating in hostilities and that collateral damage is not excessive. And he noted that law-of-war principles “do not forbid the use of stealth or technologically advanced weapons” — an apparent reference to drones.

More broadly, Holder argued that the targeting of specific senior belligerents in wartime in not unusual, and noted the 1943 U.S. tracking and shooting down of the plane carrying Japanese Adm. Isoroku Yamamoto, the commander of the attack on Pearl Harbor.

He said that “because the United States is in an armed conflict, we are authorized to take action against enemy belligerents under international law . . . and our legal authority is not limited to the battlefields of Afghanistan.”

Holder said he rejected any attempt to label such operations “assassinations.”

“They are not, and the use of that loaded term is misplaced,” he said. “Assassinations are unlawful killings. Here, for the reasons I have given, the U.S. government’s use of lethal force in self-defense against a leader of al-Qaeda or an associated force who presents an imminent threat of violent attack would not be unlawful — and therefore would not violate the executive order banning assassination or criminal statutes.”

Holder said “it is preferable to capture suspected terrorists where feasible — among other reasons, so that we can gather valuable intelligence from them — but we must also recognize that there are instances where our government has the clear authority — and, I would argue, the responsibility — to defend the United States through the appropriate and lawful use of lethal force.”