Prisoners’ Right to Read: A New Interpretation to the Library Bill of Rights
Adopted June 29, 2010, by the ALA Council.

Above-linked document begins:

The American Library Association asserts a compelling public interest in the preservation of intellectual freedom for individuals of any age held in jails, prisons, detention facilities, juvenile facilities, immigration facilities, prison work camps and segregated units within any facility. As Supreme Court Justice Thurgood Marshall wrote in Procunier v Martinez [416 US 428 (1974)]:

When the prison gates slam behind an inmate, he does not lose his human quality; his mind does not become closed to ideas; his intellect does not cease to feed on a free and open interchange of opinions; his yearning for self-respect does not end; nor is his quest for self-realization concluded. If anything, the needs for identity and self-respect are more compelling in the dehumanizing prison environment.

See also the OIF Blog for background information