Mike,
"A crowd of travellers standing outside the terminal at curbside check-in would be a nice target for a car bomb or well-executed drive-by. I suspect they're trying to address this issue."
Granted, but a similar-sized crowd standing around waiting to get into a movie isn't?
Point being that there are too many "soft targets" to list & searching cars coming into an airport isn't doing anything to stop any of it - any more than there's any protection for all the other soft targets. Searches at airports get "priority" merely because planes were used to do in the 2Towers & have "visibility" to make us feel safer.
Can you say boxcutters? That & the will to use them+ to their desired result allowed 911 to happen. No security apparatus can ever prevent a similar occurance. If it isn't another plane, it will be something else.
Even with a complete/total lock-down on everything, still something can (& will) get through & will allow another "event."
Still, for all I can find regards fed & CO law, it isn't illegal to possess a legally carried firearm (CO is legal to CCW in any mass-transit facility with proper "license") anywhere in & around an airport, long as you don't try to walk through "security." Read that last as the "check point." Up to, by all accounts, you're good to go.
Pena Blvd, the road to DIA, has signs (well before 911) that states "vehicles subject to search/FAA Area, yada." OK, well & good, & I'm all for keeping the random Mad Car Bombers from accessing the 'port, but I'd just betcha that any of these fine young men (& wimmons) don't have any clue as to what the laws are & they'd jack you up toot sweet for having a legally possessed firearm if "breaking the barrier."
Just a consideration & mention.