Pat,
Flyertalker KarenH, an Australian, got into a tiff in Atlanta recently regarding the size of her (non quart-sized, international litre-based) plastic ziplock bag. She'd already gone through a few US airports successfully, and when stopped in Atlanta, objected.

Apparently a LEO was called, and as she eventually called the LEO a Nazi, she was arrested for disorderly conduct and emprisoned for 7 1/2 hours.

Rita