SAN FRANCISCO -- The Justice Department won't acknowledge whether federal rules demanding airline passengers show identification before flying even exist, according to court documents filed with a federal appeals court here Monday.

The Bush administration told the 9th U.S. Circuit Court of Appeals that air-travel security initiatives are a matter of national security, and therefore should not be available for public inspection.

The Justice Department documents were lodged in response to a lawsuit brought by a California man, who sued the government and airlines. The man, Oakland resident John Gilmore, a Libertarian who made millions as a founding employee of Sun Microsystems, wants to see the law that he says violates his rights to assemble freely.

The government had requested that it file its case under seal, but on Sept. 10, the court ordered it open for public inspection.

The Justice Department, however, urged the appeals court Monday to reconsider its position.

"In this case, plaintiff alleges the existence of a security directive issued by the federal government relating to airline security procedures, and he challenges the constitutionality of that directive," government attorneys Douglas Letter and Joshua Waldman wrote the appeals court.

"In order to protect air travel security," they added, "a federal statute and accompanying regulations prohibit defendants from disclosing any such directive in open court, to plaintiff or to plaintiff's counsel."

James Harrison, Gilmore's attorney, said the case was about "the ability to travel freely within the United States without having to show your identification at every turn."

He added that laws "are being applied, yet when the citizen asks to see the law that is being applied, he's met with, 'Sorry that's classified."'

Justice Department spokesman Charles Miller declined to elaborate on the government's filing, saying it "states what we want to say."

A federal judge in San Francisco dismissed Gilmore's challenge without determining whether such a law existed, and Gilmore appealed.

On July 4, 2002, Southwest Airlines employees at Oakland International Airport barred Gilmore from boarding a flight to Baltimore after he refused to produce government-issued, photo identification.

He also refused to allow security personnel to pat him down and search through his luggage instead of producing the identification.

Gilmore went through a similar experience with United Airlines employees at San Francisco International Airport later that day. Both airlines said they were following federal directives.