WASHINGTON (CNN) -- The U.S. Supreme Court on Tuesday left in place a law that allows the Justice Department to stop suits against telecommunications companies for participating in wiretaps of potential terrorists.
The ruling was a key setback for civil libertarians challenging the broader powers of government since the September 11, 2001, attacks on the United States to use electronic surveillance to track potential threats in the name of national security.
The Justices declined to take up a challenge to the once-secret domestic eavesdropping program under the Foreign Intelligence Surveillance Act -- this one involving the monitoring of information moving into and out of the United States.
Previous petitions dealing with alleged abuses of the surveillance law also have been rejected by the court. Another case will be heard later this month.
In this case, Verizon Communications, Sprint Nextel, and AT&T were accused of privacy violations by assisting the government with intelligence gathering following the hijack attacks on New York and Washington.
The law had previously required the government to justify a national security interest before any phone calls and emails originating in another country could be monitored. A federal judge had to sign any search warrant. But President George W. Bush secretly suspended that requirement following the attacks.
After "warrantless wiretapping" was exposed, the president and supporters in Congress moved to amend the law, which defenders contend is designed to target only foreigners living outside the United States.
The retroactive immunity was challenged in the class action suit turned aside by the high court on Tuesday.
Privacy groups worry such electronic dragnets could easily and unknowingly intrude on the privacy rights of U.S. citizens. The government calls that "speculation" but cites national security in refusing to provide specifics.
The lawsuits launched by a number of telecommunications customers cited the testimony of Mark Klein, a retired AT&T engineer from San Francisco, who claimed company executives gave government access to internal hardware.
The result, he testified, was "vacuum-cleaner surveillance of all the data crossing the Internet, whether that be people's email, web surfing or any other data."
In an appeal, the Electronic Frontier Foundation and the American Civil Liberties Union said the retroactive immunity was unconstitutional because it gave unfettered power to the executive branch -- namely the attorney general and the director of national intelligence -- to decide it could not be held accountable in court.
Attorney General Eric Holder has used that power to block about 30 suits.
Justice Samuel Alito did not participate in the appeal. Previously released financial records show he has owned telecommunications stock and likely recused himself to avoid the appearance of a conflict of interest.
The Supreme Court will hear a related challenge to the domestic surveillance program on October 29.
The larger issue involves the constitutionality of the government's electronic monitoring of targeted foreigners.
A federal appeals court in New York last year ruled domestic plaintiffs who deal with global clients and co-workers reasonably feared the government was reading and hearing their sensitive communications. Those groups took costly measures to avoid such intrusions.
The question to be addressed is whether certain Americans have "standing" to challenge the federal law without a specific showing they have been monitored.
Other lawsuits over the surveillance program that raise various legal issues are pending in lower courts.
The case rejected Tuesday is Hepting v. AT&T (11-1200). The case to be heard later this month is Clapper v. Amnesty International USA (11-1025)