Gilmore is asking just how much citizens are giving up when they hand their driver's licenses to a third party, in this case an airline, where it is put into a database they cannot see, to meet a law that, as it turns out, they are not allowed to read.
Gilmore will show ID for an international flight because he doesn't expect to set the rules for other nations.
“I will show a passport to travel internationally. I'm not willing to show a passport to travel in my own country,” Gilmore said. “I used to laugh at countries that had internal passports. And it's happened here and people don't even seem to know about it.”
–http://www.postgazette.com/pg/05058/462446.stm
PS – attention Firefox users (and if you're not using firefox, whyinhell not??) I highly recommend the QuickNote extension.