Attorney General Eric H. Holder Jr. on Monday plans to provide the most detailed account to date of the Obama administration’s legal rationale for killing U.S. citizens abroad, as it did in last year’s airstrike against an alleged al-Qaeda operative in Yemen, officials said.

The rationale Holder plans to offer resembles, in its broad strokes, those previously offered by lower-ranking officials. But his speech Monday will mark a new and higher-profile phase of the administration’s campaign to justify lethal action in those rare instances in which U.S. citizens, such as New Mexico-born Anwar al-Awlaki, join terrorist causes devoted to harming their homeland.

Civil libertarians and other critics have been demanding a more thorough and public accounting of the administration’s logic since the killing of Awlaki in September. Administration officials have relied on a classified opinion, written by the Justice Department’s Office of Legal Counsel, that provides a legal framework for the unusual action, but they have refused repeated requests to release it despite intense internal debate on the subject.

Holder plans to argue that the killing of an American terrorist abroad is legal under the 2001 congressional authorization of the use of military force, according to an official briefed on the speech, who spoke on the condition of anonymity to discuss its details ahead of its formal release. This official also said Holder plans to say that the U.S. right to self-defense is not limited to traditional battlefields as the government pursues terrorists who present an imminent threat.

Awlaki, 40, was a skilled propagandist and the chief of external operations for al-Qaeda’s affiliate in Yemen, which has attempted a number of terrorist attacks on the United States, according to administration officials. He had been placed on “kill lists” compiled by the CIA and and the military’s Joint Special Operations Command. Awlaki died when a joint CIA-JSOC drone operation fired missiles at him.

He was the first U.S. citizen deliberately targeted by the U.S. government.

Major address on security

The Awlaki operation was carried out after the administration requested and received the Justice Department opinion saying that targeting and killing U.S. citizens overseas was legal under domestic and international law, according to administration officials. The classified memo also included intelligence material about his operational role within al-Qaeda’s affiliate in Yemen.

Senior Obama administration officials, including John O. Brennan, the president’s counterterrorism adviser, and Harold Koh, the State Department legal adviser, have given speeches that offered a broad rationale for U.S. drone attacks on individuals in al-Qaeda and associated forces.

On Feb. 22, in a speech at Yale Law School, Pentagon General Counsel Jeh Johnson said the targeted killing of those suspected of engaging in terrorist activities against the United States, including U.S. citizens, is justified and legal. He did not mention Awlaki by name or the secret CIA drone program.

Holder’s remarks will be included in what administration officials are calling a major national security speech at Northwestern University’s law school in Chicago. The speech may not mention Awlaki by name, but his case has been central to the legal thinking on the issue and in the preparation of the text of Monday’s speech, officials said.

In the administration, there was some reluctance on the part of the intelligence community to discuss the subject publicly. But others argued that the killing of an American citizen by the U.S. government was such an extraordinary event that it required some public accounting.

The American Civil Liberties Union has asked a federal court to force the Obama administration to release legal and intelligence records related to the killing of Awlaki and two other U.S. citizens in drone attacks in Yemen last year. Samir Khan, also a U.S. citizen, was reported to have been killed in the Awlaki attack. And Awlaki’s 16-year-old son, Abdulrahman, was reportedly killed in a JSOC drone strike two weeks later.

After the killing of Awlaki, several senators called on the Obama administration to release the classified legal memo.

Sen. Dianne Feinstein (D-Calif.), chairman of the Senate Select Committee on Intelligence, said that “for both transparency and to maintain public support of secret operations, it is important to explain the general framework for counterterrorism actions.”

Sen. Carl Levin (D-Mich.), chairman of the Senate Armed Services Committee, also urged administration officials to release the memo.

Civilian vs. military custody

Holder’s speech will also outline the Obama administration’s approach to counterterrorism and the rule of law, according to an official familiar with the address. Holder will discuss the broad new waivers that President Obama issued last week that allow U.S. law enforcement agencies to retain custody of al-Qaeda terrorism suspects rather than turn them over to the military.

Holder also plans to highlight the success of the civilian court system in the prosecutions and convictions of terrorism suspects. One case he will cite as an example is that of Umar Farouk Abdulmutallab, the Nigerian who tried to bring down a U.S. commercial flight on Christmas Day 2009 by attempting to detonate a bomb hidden in his underwear. He was sentenced last month to life in prison.

Abdulmutallab was arrested by federal law enforcement agents, given his Miranda rights within an hour and processed through the civilian criminal justice system. Some Republican critics argued that Abdulmu­tallab should never have been advised of his rights to counsel and that the administration should have considered turning him over to the military to continue his interrogation.

But administration officials said that they got the intelligence they needed from him immediately and that later he provided further details on al-Qaeda in the Arabian Peninsula. Some of that information, including on Awlaki’s alleged operational role, was revealed at Abdulmutallab’s sentencing.

Prosecutors said Abdulmu­tallab was acting on the orders of Awlaki, which may have been a critical factor in the legal reasoning in the classified Justice memo justifying his killing.

Holder will also discuss the debate over whether terrorism suspects should be tried in federal criminal courts or by military commissions. The administration argues that military commissions are appropriate for a small and select group of cases but that it should have the ability to transfer some suspects at Guantanamo Bay, Cuba, to the United States for trial. Congress, however, has blocked such prosecutions.