Within the administration’s legal team there is wide consensus that it is lawful to target Mr. Awlaki. But some lawyers had disagreed on what arguments they should muster to have the lawsuit dismissed. In the end, the faction favoring a more expansive approach won out.

While the government’s brief did not confirm that Mr. Awlaki was being targeted, it contended, among other things, that his father, Nasser al-Awlaki, had no legal standing, that targeting decisions are for the executive branch to determine and that litigating the matter would jeopardize state secrets. The brief also included a classified annex.

Attorney General Eric H. Holder Jr. approved making the state-secrets argument. Matthew Miller, a Justice Department spokesman, said it was necessary in this case.

“The attorney general reformed the use of the state secrets privilege to guarantee it is only invoked when absolutely necessary, and never to cover up government wrongdoing," Mr. Miller said. "In this case, the plaintiff has demanded the government disclose a wide variety of classified information that could harm our national security. It strains credulity to argue that our laws require the government to disclose to an active, operational terrorist any information about how, when and where we fight terrorism.”

In a joint statement, the two legal groups representing Nasser Al-Awlaki -- the American Civil Liberties Union and the Center for Constitution Rights, said: “The idea that courts should have no role whatsoever in determining the criteria by which the executive branch can kill its own citizens is unacceptable in a democracy. In matters of life and death, no executive should have a blank check."