The Justice Department has asked an appellate court to keep its arguments secret for a case in which privacy advocate John Gilmore is challenging federal requirements to show identification before boarding an airplane.

A federal statute and other regulations "prohibit the disclosure of sensitive security information, and that is precisely what is alleged to be at issue here," the government said in court papers filed Friday with the U.S. Court of Appeals for the 9th Circuit. Disclosing the restricted information "would be detrimental to the security of transportation," the government wrote.

Attorneys for Gilmore, a San Franciscan who co-founded the Electronic Frontier Foundation, said the civil liberties group does not accept the government's argument and that its latest request raises more questions.

"We're dealing with the government's review of a secret law that now they want a secret judicial review for," one of Gilmore's attorneys, James Harrison, said in a telephone interview Sunday. "This administration's use of a secret law is more dangerous to the security of the nation than any external threat."

Gilmore first sued the government and several airlines in July 2002 after airline agents refused to let him board planes in San Francisco and Oakland without first showing an ID or submitting to a more intense search. He claimed in his lawsuit the ID requirement was vague and ineffective and violated his constitutional protections against illegal searches and seizures.

A federal judge earlier this year dismissed his claims against the airlines, but said his challenge to the government belonged in a federal appellate court.