A policy, and campaigns to bring the policy into practice, of the American Library Association.

Congress Shall Make No Law Respecting an Establishment of Religion, or Prohibiting the Free Exercise Thereof; or Abridging the Freedom of Speech, or of the Press; or the Right of the People Peaceably to Assemble, and To Petition the Government for a Redress of Grievances. - First Amendment of the Constitution
Essentially by arguing that freedom of speech is meaningless without freedom to hear and freedom to read the policy and campaigns are based on the Freedom to Read Statement and run by the Office for Intellectual Freedom of the American Library Association.

The key points of the Freedom to Read Statement are:

  1. It is in the public interest for publishers and librarians to make available the widest diversity of views and expressions, including those that are unorthodox or unpopular with the majority.
  2. Publishers, librarians, and booksellers do not need to endorse every idea or presentation they make available. It would conflict with the public interest for them to establish their own political, moral, or aesthetic views as a standard for determining what should be published or circulated.
  3. It is contrary to the public interest for publishers or librarians to bar access to writings on the basis of the personal history or political affiliations of the author.
  4. There is no place in our society for efforts to coerce the taste of others, to confine adults to the reading matter deemed suitable for adolescents, or to inhibit the efforts of writers to achieve artistic expression.
  5. It is not in the public interest to force a reader to accept with any expression the prejudgment of a label characterizing it or its author as subversive or dangerous.
  6. It is the responsibility of publishers and librarians, as guardians of the people's freedom to read, to contest encroachments upon that freedom by individuals or groups seeking to impose their own standards or tastes upon the community at large.
  7. It is the responsibility of publishers and librarians to give full meaning to the freedom to read by providing books that enrich the quality and diversity of thought and expression. By the exercise of this affirmative responsibility, they can demonstrate that the answer to a ``bad'' book is a good one, the answer to a ``bad'' idea is a good one.
The full text of the statement is at (it's too modern to include as full text):
http://www.ala.org/alaorg/oif/freeread.html

The statement was originally issued in May of 1953 by the Westchester Conference of the American Library Association and the American Book Publishers Council, which in 1970 consolidated with the American Educational Publishers Institute to become the Association of American Publishers.

Adopted June 25, 1953; revised January 28, 1972, January 16, 1991, July 12, 2000, by the ALA Council and the AAP Freedom to Read Committee.