The Justice Department has concluded that the National Security Agency’s program to eavesdrop on phone calls between Al Qaeda operatives and persons in America is lawful, despite a Supreme Court ruling last month denying President Bush some powers he claimed in the war on terror.

“Our initial impression is that the court’s opinion does not affect our analysis of the terrorist surveillance program,” the Justice Department’s legislative liaison, William Moschella, wrote in a letter Monday responding to an inquiry from Senator Schumer.

Many legal analysts said the Supreme Court’s June 29 decision in Hamdan v. Rumsfeld, rejecting Mr. Bush’s system of military commissions for Al Qaeda members, undercut the legal rationale the administration offered for the highly classified warrantless surveillance program, which was disclosed in December by the New York Times.

The Justice Department has argued that the use-of-force resolution passed by Congress in 2001 gave Mr. Bush implicit authority to institute the surveillance program. However, the Supreme Court’s decision in Hamdan rejected a similar argument that the military commissions were implicitly authorized by same resolution.

Mr. Moschella wrote that the legal backdrop for the NSA program suggests that it is covered by a more expansive reading that the Supreme Court gave to the use-of-force resolution when the court upheld the detention of an American-born prisoner,Yaser Hamdi, in 2004.

“We believe the reasoning of Hamdi is far more relevant to the terrorist surveillance program,” Mr. Moschella said.

The dean of Yale Law School, Harold Koh, said the Justice Department’s legal assessment “borders on frivolous.”

“Some people just can’t take a hint,” Mr. Koh told The New York Sun. “This is the kind of legal reasoning that led to their defeat in Hamdan. They quite literally do not understand the message the court was trying to send them.”

Mr. Koh said lawmakers never saw the use-of-force resolution as providing the catchall authority the administration has asserted. “There is not a single member of Congress who thought they were creating an alternative system of courts. Just as clearly, they did not think they were authorizing a widespread program of domestic surveillance,” he said.

In a related development, the chairman of the Senate Judiciary Committee, Senator Specter, sent a series of questions to the Justice Department yesterday about its efforts to investigate leaks, such as the electronic surveillance program disclosed by the Times. Mr. Specter asked Attorney General Alberto Gonzales, who is to testify to the committee next week, to take a position on congressional resolutions calling for criminal investigations of the leaks.

The senator also asked what arguments the administration used in an unsuccessful effort to convince newspapers not to run stories about an international program to track terrorist financing.