The DC Checkpoint plan I blog about below raises another interesting question: Can a police officer order you to move along -- that is, to leave the area -- without any suspicion that you've committed a crime? Stephen Henderson recently wrote a very interesting article on the topic that is worth reading if you're interested:'Move On' Orders as Fourth Amendment Seizures, recently published in the Brigham Young University Law Review.

  This topic also raises something I've long wondered about: What are the Due Process limits on criminalizing failure to obey an officer? In particular, is there a constitutional requirement that the person understands that failure to obey is a crime? Citizens generally have no idea when they have to do what an officer tells them to do, and I would think there is some sort of Due Process requirement of fair notice that the order has to be obeyed before an arrest can be made.