The Court's first explicit statement of the ldesignated public forum doctrine came in Southeastern Promotions v Conrad.  Southeastern Promotions sought permission to use Chattanooga, Tennessee's municipal auditorium for performances of the musical "Hair."  Although the auditorium had been rented for a wide variety of expressive activities prior to Southeastern's application, Chattanooga city officials refused Southeastern's request, citing Hair's nudity, tacit approval for drug use, sexual themes, and bad language.  The Court found the municipal auditorium to be a designated public forum, and the city's refusal to permit use of its auditorium to be an unconstitutional prior restraint.

The main difference between  traditional and limited public forum, for First Amendment purposes, is that the government, in dedicating the forum for expressive purposes--that is, in defining the forum--may adopt reasonable limitations on who may use the forum. (Also, government cannot ban expression completely in the traditional public forum, whereas it is under no First Amendment obligation to have opened a limited forum.) For example, the UMKC student center meeting rooms found to be a limited public forum in Widmar v Vincent could be restricted in their use to students, excluding members of the general public.  It also would be permissible to restrict use of the meeting rooms to only academic programming.  But it is impermissible, the Court said, for the university to allow students to meet for academic, social, or political purposes, but not for religious purposes.

Rosenberger v University of Virginia demonstrates that a limited public forum need not be a physical place.  In Rosenberger, the Court found that Virginia had created a limited public forum when it established a fund that would cover the cost of publications by eligible student groups.  Once having created such a forum (which, of course, it was under no obligation to do), Virginia could not refuse funding to a student organization because of the overtly religious nature of its publication.

In Christian Legal Society v Martinez (2010), the Court considered a decision of the Hastings Law School (a public law school in California) to deny the benefits that come from being a registered student organization (including funding, use of student bulletin boards, etc) to the school's chapter of the Christian Legal Society because it denied membership to students who "engage in unrepentant homosexual conduct" or do not share the religious convictions described in the organization's Statement of Faith.  By a 5 to 4 vote, the Court held that Hastings could, consistent with the First Amendment, enforce a policy that registered student organizations admit "all comers."  Such a policy, the Court decided, violates neither principles of limited-forum analysis or the associational rights of the CLS.