In conjunction with this week's Worldwide Developers Conference, Apple has updated its App Store Review Guidelines, and part of the new approval process includes a section that prohibits the inclusion of DUI checkpoints in iOS apps.
Section 22.8 states:
Apps which contain DUI checkpoints that are not published by law enforcement agencies, or encourage and enable drunk driving, will be rejected.
The updated terms come a few months after a group of U.S. Senators sent letters of concern to Apple, Google and RIM, asking the smartphone companies to remove any and all apps that would inform users of DUI checkpoints.
Personally, don't see why anyone needs DUI checkpoint apps, but fuck, Apple - It's not your job to police this stuff.