The C.I.A. has placed the American-born cleric Anwar al-Awlaki on a list for killing. The notion that the government can, in effect, execute one of its own citizens,an American, born in New Mexico, far from a combat zone, with no judicial process and based on secret intelligence, makes some legal authorities deeply uneasy.

Harold Koh, the State Department’s legal adviser, approves under the general principle of self-defense. By those rules, he said, such targeted killing was not assassination, which is banned by executive order.

Mr. Holder signaled the abrupt shift of tone as the administration’s proposaed to ask Congress to loosen the Miranda rule. It comes against the backdrop of sharp criticism by Republicans who have argued that terrorism suspects — including United States citizens like Faisal Shahzad, the suspect in the Times Square case — should be imprisoned and interrogated as military detainees, rather than ordinary criminal defendants. It generally forbids prosecutors from using as evidence statements made before suspects have been warned that they have a right to remain silent and to consult a lawyer.