Mainstream Loudoun et al. v. Board of Trustees of the Loudoun County Library et al.

The ruling upheld constitutional rights of library users by affirming that First Amendment freedoms fully apply to public library Internet access. The decision set a legal standard for assessing Internet use restrictions in future cases. With the clarification of First Amendment protections applied to public Internet use, libraries searched for legal means to control access, particularly for children who hold fewer First Amendment rights.

The rapid growth of the Internet in the 1990s and its use in public libraries raised new complex legal and policy questions. Clearly, the shear volume of information on the Internet meant that much unreliable, illegal, and clearly dangerous material was more accessible to individuals. By the late 1990s, the computer industry had developed software capable of screening Internet material considered "inappropriate." About 15 percent of public libraries in the United States installed the filters on at least some their computer terminals according to a survey by the American Library Association (ALA). Such filter programs were immediately criticized by civil libertarians charging the programs, while ineffective in blocking out all undesirable materials, did block out much material considered appropriate for viewing. The ALA argued that users of the Internet in public libraries were the only ones who should determine what is appropriate for them to view. On the other hand, a Ohio library's funding was threatened by community members unless the library installed filters. Few libraries fully supported the ALA position.

The U.S. Supreme Court, in the unanimous 1997 Reno v. ACLU ruling striking down key provisions of the Communications Decency Act, noted the potential use of such software as a legally preferable alternative to legislation limiting speech. In response, various states considered legislation promoting the use of such software, or other means of content restriction in public schools and libraries.