Access to knowledge and information has been ensured for centuries through libraries, which come in many forms: national, public, governmental, presidential, children's, digital, specialized, and others, as analyzed in the first chapter of this book. The development of library collections is a complex process, which is primarily regulated by a series of legal rules of different hierarchy of sources of law, as well as by a series of ethical rules of librarianship. The development of these collections is first and foremost controlled as to whether these legal and ethical rules that regulate them are followed - if the development of the collections is based, that is, on the solid legal and ethical foundations on which it should be based. If not, the entire structure of the library collection suffers from its foundations, and no matter how effectively and quickly the other tasks in the library are performed, such as ordering, market research, research on the needs of library users, evaluation of the library, and others, the collection is not only problematic, but also constitutes a focal point of risk of violation of fundamental rights of its users. The protection of these fundamental rights of access to information, speech and expression, teaching and research, equality and intellectual freedom equally concerns public and private libraries in Greece. This work aims to describe and analyze the types of libraries, the fundamental rights that apply to the development of their collections, and the laws, regulations, and policies that regulate them in Greece, presenting relevant examples from the Greek and international field.