In my opinion a really good public library would be able to offer its users the total services of all the designated roles for public libraries. In reality, all the roles are important but may be adopted to various degrees, depending on library funding. Most libraries will choose one to two primary roles and one to two secondary roles to support depending on the library's size and budget. Publicly supported library service is based on the constitutional right of freedom of expression. Public libraries are public forums for accessing information.
Guidelines exist to protect access and the regulation of user behavior.
The American Library Association, currently under fire for many of these policies, has adopted policies like the Library Bill of Rights, the ALA code of professional ethics to ensure access to library services and materials. Other laws, constitutional, federal, state, and local, serve the same purpose. Unfortunately, many of these are currently under assault from interest groups, from the right and also from the left. The guidelines established by the ALA on user behavior and library usage require that rules and policies be reasonable and narrowly drawn, but not overly restrictive, should not violate the Library Bill of Rights and should attempt to balance competing interests. Most importantly, in my opinion, they should be based on actual behavior and not upon arbitrary distinctions between individuals and classes of individuals.