I'll say it again. If a library opens a meeting room, exhibit space, bulletin board, pamphlet racks etc. up to the general public, it may never restrict based on viewpoint. A lawsuit was just filed against a library that cancelled a pro-life film because of the possibility of disturbance.
Confirming our telephone conversation yesterday afternoon, we have cancelled the room reservation placed by your group, 40 Days for Life, at MCPL on April 3, 2011. This is due to the fact that we cannot permit a program that would invite the possibility for a disturbance on library property. 40 Days for Life v Illick - complaint
Justia has all of the court documents. A surprisingly good guide to this issue was written by the Anti-Defamation League, and I recommend reading it. I say surprising, because the ADL's own interest is in civility and limiting speech, yet it recognizes the core First Amendment principles that restrict the government from restricting speech, even if it might provoke a disturbance.
This issue was my real awakening, back many, many a year ago, when I was in law school and read the Concerned Women of America case. I realized that my own library had restricted religious groups from meeting in the library, and that this should have been a lawsuit. We fortunately ducked that one, but I've been on a mission ever since to make sure public libraries know that they are government actors, are bound by the First Amendment, and may not restrict - ever - based on the public viewpoint. I've written about this in The Library's Legal Answer book, and on this blog. Yet perhaps not everyone reads my book and blog, so please spread the message.
Eugene Volokh has a good post, noting thatthe library had concerns that a protest was being planned via Facebook. Nevertheless, the hecker's veto has long been discredited. As Volokh states, "a worry that the viewpoint of the speakers will bring in protesters — who can of course be required to comply with library rules, such as by staying on the sidewalk outside and being quiet enough to disrupt the use of the library — does not, I think, justify restrictions, either. See this post about a similar case at a university (though there the university was worried about violence, and not just protests, and required the payment of extra fees for security rather than just excluding the speaker outright)."
There have been cases in libraries as well, in which a library has required extra fees for security. Settlement by library - no fees required.