In his first public comment on the matter, Mr. Bush said he "strongly disagrees" with the judge's ruling and believes the program is needed to protect the nation, CBS News White House correspondent Mark Knoller reports.
"I would say that those who herald this decision simply do not understand the nature of the world in which we live. I strongly disagree with this decision," he told reporters at the presidential retreat in Camp David.
"We strongly believe it's constitutional and if al Qaeda is calling into the United States we want to know why they're calling," he said.
The Justice Department is appealing the ruling.
On Thursday, U.S. District Judge Anna Diggs Taylor in Detroit became the first judge to strike down the National Security Agency's program, which she says violates the rights to free speech and privacy as well as the separation of powers enshrined in the U.S. Constitution.
"Plaintiffs have prevailed, and the public interest is clear, in this matter. It is the upholding of our Constitution," Taylor wrote in her 43-page opinion.
The parties in the lawsuit agreed to a delay of the injunction to stop the surveillance until they can argue before Judge Taylor for a stay pending appeal, CBS News producer Beverley Lumpkin reports.
U.S. Attorney General Alberto Gonzales said the surveillance program has been "very effective" in protecting Americans.
"We believe very strongly that the program is lawful. ...," Gonzales said in Washington. "We respectfully disagree with the decision of the judge and have appealed the decision."
The government argued that the program is well within the president's authority, but said proving that would require revealing state secrets.
The ACLU said the state-secrets argument was irrelevant because the Bush administration already had publicly revealed enough information about the program for Taylor to rule.
"At its core, today's ruling addresses the abuse of presidential power and reaffirms the system of checks and balances that's necessary to our democracy," ACLU executive director Anthony Romero said in a conference call with reporters.
He called the opinion "another nail in the coffin in the Bush administration's legal strategy in the war on terror."
The Justice Department said it had appealed Taylor's ruling because the program is "an essential tool for the intelligence community in the War on Terror."
"In the ongoing conflict with al Qaeda and its allies, the President has the primary duty under the Constitution to protect the American people," the department said in a statement. "The Constitution gives the President the full authority necessary to carry out that solemn duty, and we believe the program is lawful and protects civil liberties."
Taylor's ruling won't take immediate effect. The Justice Department said it had reached an agreement with the ACLU to postpone implementing the order until Taylor hears its request for a stay pending appeal. A hearing on the motion was set for Sept. 7, Snow said.
While siding with the ACLU on the surveillance issue, Taylor dismissed a separate claim by the group over NSA data mining of phone records. She said not enough had been publicly revealed about that program to support the claim and further litigation would jeopardize state secrets.
The lawsuit alleged that the NSA "uses artificial intelligence aids to search for keywords and analyze patterns in millions of communications at any given time." Multiple lawsuits have been filed related to data mining against phone companies, accusing them of improperly turning over records to the NSA.
However, the data mining was only a small part of the Detroit suit, said Ann Beeson, the ACLU's associate legal director and the lead attorney on the case.
In the decision, Judge Taylor quoted Justice Earl Warren from the 1967 case, U.S. v Robel, Lumpkin reports.
"Implicit in the term 'national defense' is the notion of defending those values and ideas which set this Nation apart. ... It would indeed be ironic if, in the name of national defense, we would sanction the subversion of ... those liberties ... which makes the defense of the Nation worthwhile," Taylor wrote.