WASHINGTON – The Supreme Court dealt a setback Tuesday to civil rights and privacy advocates who oppose the Bush administration’s warrantless wiretapping program.

The justices, without comment, turned down an appeal from the American Civil Liberties Union to let it pursue a lawsuit against the program that began shortly after the Sept. 11 terror attacks.

The action underscored the difficulty of mounting a challenge to the eavesdropping, which remains classified and was confirmed by President Bush only after a newspaper article revealed its existence.

“It’s very disturbing that the president’s actions will go unremarked upon by the court,” said Jameel Jaffer, director of the ACLU’s national security project. “In our view, it shouldn’t be left to executive branch officials alone to determine the limits.”

The Terrorist Surveillance Program no longer exists, although the administration has maintained it was legal.

The ACLU sued on behalf of itself, other lawyers, reporters and scholars, arguing that the program was illegal and that they had been forced to alter how they communicate with foreigners who were likely to have been targets of the wiretapping.

A federal judge in Detroit largely agreed, but the 6th U.S. Circuit Court of Appeals dismissed the suit, saying the plaintiffs could not prove their communications had been monitored and thus could not prove they had been harmed by the program.

The government has refused to turn over information about the closely guarded program that could reveal who has been under surveillance.

ACLU officials described the situation as a “Catch-22” because the government says the identities of people whose communications have been intercepted is secret. But only people who know they have been wiretapped can sue over the program.

A lawsuit filed by an Islamic charity met a similar fate. The 9th U.S. Circuit Court of Appeals last year ruled against the Oregon-based U.S. arm of the Al-Haramain Islamic Foundation, concluding that a key piece of evidence is protected as a state secret.

In that case, the charity alleged the National Security Agency illegally listened to its calls. The charity had wanted to introduce as evidence a top-secret call log it received mistakenly from the Treasury Department.

A separate lawsuit against telecommunications companies that have cooperated with the government is pending in the San Francisco-based appeals court.

Last July, U.S. District Judge John Vaughn Walker declined to dismiss lawsuits filed by Maine and four other states seeking information on a federal government warrantless wiretap program, keeping the cases alive pending the appeals court decision.

Lawyers for New Jersey, Vermont, Maine, Missouri and Connecticut said they were pursuing complaints by consumers who argue their privacy would have been violated if phone records were turned over to the National Security Agency without their consent.

A U.S. district court also is examining whether the warrantless surveillance of people in the United States violates the law that regulates the wiretapping of suspected terrorists and requires the approval of a secret court.

The administration announced in January 2007 that it would put intercepts of communications on U.S. soil under the oversight of that court, the Foreign Intelligence Surveillance Court.

The ACLU, in urging the justices to consider its case, said that because the administration voluntarily ended the warrantless wiretapping, it could easily restart it.

The administration acknowledged the existence of the program in late 2005, after The New York Times published an article about it.

The White House said the monitoring was necessary because the 1978 Foreign Intelligence Surveillance Act left dangerous gaps in the government’s eavesdropping authority.

Last August, Congress made temporary changes to FISA that made the warrantless wiretapping legal in some instances and also extended immunity from lawsuits to telecommunications companies that help with the intercepts.

Those changes expired over the weekend, amid disagreements between congressional Democrats and President Bush over the immunity issue.

Existing wiretaps can continue and any new surveillance the government wants to institute has to follow the FISA rules, which could require court warrants.

Shenna Bellows, executive director of the Maine Civil Liberties Union, urged Sens. Olympia Snowe and Susan Collins of Maine to rethink their recent votes on the telecom immunity bill in light of the Supreme Court’s ruling Tuesday.

“Because of this ruling, it is now doubly important that Congress not pass a final intelligence bill that includes immunity for the telecom companies,” Bellows said in a statement. “Today the Supreme Court closed a door on judicial review of executive abuse of power; Congress should not voluntarily abdicate its own power of review and oversight.”