John Gilmore, the high-tech millionaire unhappy over a burgeoning demand for identification papers from American citizens, gets his day in court today on a 4-year-old challenge to regulations requiring airline passengers to show ID.

John Gilmore Previous coverage Millionaire John Gilmore stays close to home while making a point about privacy (2/27/05)

Mr. Gilmore, 50, who grew up in Bradford, McKean County, will argue before the 9 th Circuit Court of Appeals in San Francisco today that federal agencies have no legal right to require ID from passengers without probable cause to believe they are committing a crime.

The Department of Homeland Security, on the other hand, has argued in court to keep the regulations requiring ID sealed from public examination and only last year acknowledged that the rule even exists. The Transportation Security Administration, which oversees air safety, classifies the regulations as sensitive security information and says they should not be required to provide the federal regulations requiring ID.

Mr. Gilmore's refusal to show identification for domestic flights has left him a multimillionaire unable to easily travel long distances inside the United States. At the same time, he has flown overseas from his home in San Francisco.

"I accept that passports are needed to travel between countries. I don't accept that I need a passport to travel in my own country," Mr. Gilmore said yesterday. He was the subject of a lengthy profile earlier this year in the Pittsburgh Post-Gazette.

Mr. Gilmore studied computing and programming on his own while a youngster in Bradford, sometimes visiting the computer laboratory at the nearby University of Pittsburgh at Bradford. He eventually went on to become the top programmer for Sun Microsystems. Early stock holdings in the firm made him a multimillionaire.

Neither Joshua Waldman, a Department of Justice attorney arguing the government's case, nor a spokesman for the department replied to repeated requests for comment yesterday.

In its earlier arguments, the government asked to submit the rules governing the ID requirement before the court under seal. Government lawyers have not defended the law, nor acknowledged its existence, but have asked that if the case is argued, it be done outside of public view for national security reasons.

"I think we have a significant chance of winning it," Mr. Gilmore said yesterday. "It really depends on what parts of the case the government chooses to focus on. If the government is successful into distracting them from the [identification] and travel issues into the jurisdictional issues of which court should look at this and the secret law, we're more likely to lose."