A U.S. law that allows telecom carriers to be granted immunity in some suits alleging illegal government surveillance is unconstitutional, two civil-rights groups argued late Thursday.

In a brief filed in U.S. District Court in San Francisco, the Electronic Frontier Foundation and local affiliates of the American Civil Liberties Union argued that the FISA Amendments Act (FAA) violates the separation of powers in the U.S. government among the president, lawmakers and the courts. FAA is an extension of the Foreign Intelligence Surveillance Act, which provides for a secret court to approve certain kinds of surveillance for national security. The groups' challenge is set to be heard Dec. 2.

EFF sued AT&T in 2006, alleging that the Bush administration had been conducting an illegal, warrantless wiretapping program with AT&T's help. The suit was a class action on behalf of AT&T's customers, whom the EFF said had suffered an invasion of privacy.

The wiretapping that allegedly was launched in the wake of Sept. 11 was overly broad, the EFF argued. The government has tried to keep the suit from being heard, arguing that it would endanger the country by bringing sensitive state secrets into the open. Several similar lawsuits have been consolidated before Judge Vaughn Walker at the U.S. District Court in San Francisco.

Earlier this year, Congress passed the FAA, which allows for carriers to be granted immunity from such suits. The law only required the U.S. attorney general to certify that the surveillance was allowed by certain laws, that the carriers had been given written directives that the surveillance was legal, or that the surveillance didn't take place as alleged, said Kevin Bankston, a senior staff attorney at EFF.

Attorney General Michael Mukasey filed both a public and a secret certification last month, and the Bush administration asked Judge Walker to dismiss the lawsuits. EFF and the ACLU affiliates, along with other parties in the lawsuits, filed the brief Thursday to keep the cases alive. After the Dec. 2 hearing, Bankston expects Judge Walker to decide in a timely manner whether to dismiss the suits. This is likely to be followed by an appeal from the losing side, Bankston added.

Giving the attorney general the power to issue that certification turns him into both judge and jury, Bankston said. Determining whether AT&T can be sued for alleged participation in illegal surveillance is the job of the courts, not Congress or the executive branch, he said.

"It strains credulity to believe that the same Attorney General who argued that immunity must be granted has fairly and completely weighed the interests of our clients," EFF Staff Attorney Ann Brick said in a prepared statement.