The World Intellectual Property Organization (WIPO) has released Scoping Study on Copyright and Related Rights and the Public Domain.
Here's an excerpt:
Protection of the public domain comprises two steps, as laid down by the [WIPO] Development Agenda: first, identifying the contours of the public domain, thereby helping to assess its value and realm, and, second, considering and promoting the conservation and accessibility of the public domain.
The present study will follow the same direction as it will first assess the scope of the public domain, as defined by copyright laws, history and philosophy, before turning to the issue of its effectiveness and greater availability to the public and society at large. This will lead to the formulation of some recommendations that, by viewing the public domain as material that should receive some positive status and protection, might help to support a robust public domain, as advocated by the Development Agenda.