During his speech, more than a dozen students staged a silent protest by turning their backs to Gonzales, reports CBS News' Stephanie Lambidakis. Five students wearing black hoods unfurled a banner with a quote from Benjamin Franklin: "Those who would sacrifice liberty for security deserve neither."
Speaking to students at Georgetown University law school, Gonzales said a 15-day grace period allowing warrantless eavesdropping under the Foreign Intelligence Surveillance Act demonstrates that Congress knew such surveillance "would be essential in wartime."
Gonzales was supplying legal arguments to the president's comments Monday that the effort should be called a "terrorist surveillance program."
Before his appearance at Georgetown, Gonzales said in a television interview that some congressional leaders told the administration in 2004 that it would not be possible to write legislation regarding the warrantless surveillance effort without compromising its effectiveness.
"We did go to certain members of the congressional leadership a year and a half ago," Gonzales said on The Early Show.
During his remarks in a packed law school lecture room at Georgetown, the attorney general also said the legal standard the administration uses in deciding whether to carry out surveillance on people with suspected al Qaeda ties is equivalent to the standard required for complying with the Fourth Amendment, which bans unreasonable searches and seizures.
The reasonable basis standard, said Gonzales, "is essentially the same as the traditional Fourth Amendment probable cause standard."
Stephen Saltzburg, a law professor at George Washington University, said that Gonzales' comments do not explain why the administration doesn't go to the Foreign Intelligence Surveillance Court to obtain warrants.
"If they are using a probable cause standard, they would have no problem going to the FISA court," said Saltzburg. "The executive might think there's a reasonable basis. Courts might not agree."
Georgetown University law professor David Cole said the reasonable basis standard is not equivalent to probable cause.
Moreover, said Cole, Gonzales' comments seem to conflict with those on Monday by Air Force Gen. Michael Hayden, principal deputy director of national intelligence.
Hayden said that when weighing whether to proceed with surveillance under the president's program, "the trigger is quicker and a bit softer than it is" with FISA.
Justice Department spokeswoman Tasia Scolinos said there is no conflict between the statements of Gonzales and Hayden and that "it is really just a matter of speed; as the AG said, the standards are essentially the same."
In his address, Gonzales said, "I keep hearing, 'Why not FISA?' Why didn't the president get orders from the FISA court?
"It is imperative for national security that we can detect reliably, immediately and without delay whenever communications associated with al Qaeda enter or leave the United States."
Gonzales told his audience: "You may have heard about the provision of FISA that allows the president to conduct warrantless surveillance for 15 days following a declaration of war. That provision shows that Congress knew that warrantless surveillance would be essential in wartime."
Sharply disagreeing, George Washington University law professor Jonathan Turley said FISA's purpose "was never to grant warrantless surveillance for the war."
"While Congress saw some need to loosen the standard in the initial days of a war, it wanted the president to comply with FISA in carrying out surveillance in the United States," Turley said.
The attorney general said the program is limited in scope, and he blamed the news media for suggesting otherwise.
"These press accounts are in almost every case, in one way or another, misinformed, confusing or wrong," said Gonzales. "And unfortunately, they have caused concern over the potential breadth of what the president has actually authorized."