A GW law professor's doormat sitting in the hall outside his office. (Thumbnail at right shows the same thing w/a little more context.) I think this might be the best doormat I've ever seen! I mean, “come back with a warrant” is basically the default—cops are never supposed to enter a “home” (interpreted broadly at times, such as if you rent a hotel room in your name that is your “home” while you're there) w/out a warrant or special circumstance, but still, it's a great message for them and a reminder to you if you open your door and see cops there that you should make them get a warrant.

An office is not a home for these purposes, and I doubt this professor has the right to require a warrant before allowing the police to enter his office, but they probably would need a warrant to search it. Of course, someone at GW may be able to give consent to search which would overrule any of the professor's objections, but I'm not sure about that.

I'm not a lawyer, you know. ;-)