I came across this article from a blog I read on a regular basis that is written by someone who teaches at the University of Illinois: “Beware the Button Police,” from Inside Higher Ed. Here are the opening paragraphs:
Sporting an Obama or McCain button? Driving a car with one of the campaigns’ bumper stickers? You might need to be careful on University of Illinois campuses.
The university system’s ethics office sent a notice to all employees, including faculty members, telling them that they could not wear political buttons on campus or feature bumper stickers on cars parked in campus lots unless the messages on those buttons and stickers were strictly nonpartisan. In addition, professors were told that they could not attend political rallies on campuses if those rallies express support for a candidate or political party.
Of course, this kind of rule is goofy for all sorts of reasons, and it would never ever fly at EMU. I can’t imagine the grievance spasms from the various unions on campus, and with good cause. It seems like a completely unenforceable rule at UI as well.
Having said that, isn’t there a difference between a bumper sticker and button or something else I might take into a classroom? I mean, I have a couple of different Obama stickers on my car (along with many MANY other stickers), but my students don’t generally follow me out to my car. They certainly don’t do that during class. On the other hand, if I sport an Obama t-shirt or button to class, doesn’t that send a different kind of message?

Sounds like the City of Ypsilanti’s rules for public comment.