DETROIT - A federal judge ordered the Bush administration on Thursday to halt the National Security Agency"s program of domestic eavesdropping, saying it violated the U.S. Constitution.

The ruling marked a setback for the Bush administration, which has defended the program as an essential tool in its war on terrorism.

U.S. District Judge Anna Diggs Taylor said the warrantless wiretapping under the "Terrorist Surveillance Program" violated free speech rights, protections against unreasonable searches and the constitutional check on the power of the presidency.

"There are no hereditary kings in America and no powers not created by the Constitution," Taylor said in a 44-page ruling.

The NSA program has been widely criticized by civil rights activists and raised concern among lawmakers, including some in President George W. Bush"s own Republican Party, who say the president may have overstepped his powers by authorizing it.

The government had asked for the lawsuit brought by the American Civil Liberties Union to be thrown out, arguing that any court action on the case would jeopardize secrets in the war on terrorism.

The Justice Department had no immediate comment. The ACLU said it expected the Bush administration to seek an immediate stay on the federal court order pending an appeal before the 6th U.S. Circuit Court of Appeals.

"We think the program is unconstitutional and we are hopeful and confident that any district or appellate court who looks at it seriously will agree with that," said ACLU attorney Jameel Jaffer.

Bush authorized the NSA program after the September 11 attacks on the United States, and it became public last year.

The program allows the government to eavesdrop on the international phone calls and e-mails of U.S. citizens without obtaining a warrant, if those wiretaps are made to track suspected al Qaeda operatives.

But Taylor ruled that by skirting the process of obtaining warrants, the Bush administration had violated the terms of a 1978 surveillance law, the Foreign Intelligence Surveillance Act, or FISA.

FISA requires warrants for individual eavesdropping on suspects inside the United States.

Taylor said the government"s arguments in support of the program appeared to imply that Bush"s role as commander in chief of the U.S. armed forces gave him "the inherent power to violate not only the laws of the Congress but the First and Fourth Amendments of the Constitution itself."

Civil rights activists welcomed the decision.

"The ruling of the judge is not only a victory for the American Muslim community but a victory for the entire American population," said Dawud Walid, executive director of the Council on American-Islamic Relations for Michigan, which joined the ACLU as a plaintiff in the lawsuit.

"America is built on the principles of civil liberty and equal protection for all American citizens, regardless of ethnicity and race," he said.

The ACLU lawsuit was filed on behalf of scholars, attorneys, journalists and non-profit groups that regularly communicate with people in the Middle East and believe that their phone calls and e-mail had been intercepted by the U.S. government.

A similar suit brought by the Center for Constitutional Rights is pending in federal court in New York. The judge in that case is set to hear arguments on September 5.

Additional reporting by Jui Chakravorty, Claudia Parsons in New York, Frances Kerry in Washington