State law determines whether an entity is a public library. It would be a monumental task to identify all local laws relating to libraries in some states.
Because of the unique nature of the evolution of the library as a public service, some entities may be operating under laws which have been “grandfathered and are no longer on the books. In these cases, provisions for library governance and structure may vary slightly from the state descriptions.
What is a Public Library?
"The Federal State Cooperative System (FSCS) defines a public library as follows: A public library is established under state enabling laws or regulations to serve the residents of a community, district, or region. A public library is an entity that provides at least the following:
An organized collection of printed or other library materials, or a combination thereof
A paid staff to provide and interpret such materials as required to meet the informational, cultural, recreational, and/or educational needs of a clientele
An established schedule in which services of the staff are available to clientele
The facilities necessary to support such a collection, staff and schedule.
Association Libraries
The structure of Association libraries...are so diverse that one would have to examine each library on an individual basis using charters, articles of incorporation, and so forth. Funding for these types of libraries is derived from local, state and federal appropriations, and, in many cases, private contributions and funds from an original endowment or trust tired.
Library Branches
"The term 'branches' refers to an auxiliary unit of a public library."
A branch must have all of the following [to be considered a branch]
Separate quarters
An organized collection of library materials
paid staff
regularly scheduled hours
Other Library Types
Special libraries - are in specialized environments, such as hospitals, corporations, museums, the military, private business, and the government
Academic libraries - serve colleges and universities
School libraries - serve students from Kindergarten to grade 12
local government law libraries
Public libraries - serve cities and towns of all types
Sources
In the following resource, chapter 2 (pp. 21-48) the legal structure and organization of public libraries in all 50 states are examined. Chapter 2 contains a state-by-state description of the legal structure and organization of public libraries. Since we do not offer legal or tax advice, this is an exceptional document to share with them as a resource for their lawyer or accountant to look over.
Resources
Library Strategies - Library Strategies Consulting Group is a nonprofit that partners with library organizations nationally and internationally to cultivate their potential so that they can better serve and strengthen their communities.
American Library Association - Tax Exempt Status
American Library Association - Tax Status Basic Rules
Tax Bandits - Article: "Are Public Libraries Considered Nonprofit Organizations?"