All around the world, cops and rent-a-cops are vigorously enforcing nonexistent anti-terrorist bans on photography in public places. If you're worried about being busted under an imaginary law, why not download these templates and print yourself an imaginary "Photography license" from the DHS? Who knows if it's legal to carry one of these — probably about as legal as taking away your camera and erasing your memory card for snapping a pic on the subway.
In the event you're stopped by overzealous law enforcement or security officials attempting to enforce fictitious laws, I've designed these fictitious and official-looking Photographer's Licenses. If you have Adobe Illustrator, you can download the EPS vector art file and print your own. You'll need a photo of yourself, and OCR (or a similar font) to fill in your personal information.