According to the blog of the Justice Department’s Access to Justice Initiative:
“The UN General Assembly formally adopted the Principles & Guidelines in December 2012, making it the first international legal document on indigent defense. The Principles & Guidelines emerged through the efforts of non-governmental organizations and member states over several years, and the Department of Justice actively supported the Principles & Guidelines throughout its adoption process…. As a secondary source of law, much like a U.S. Restatement of the Law, the Principles and Guidelines express a developing international consensus on the importance of effective legal aid systems in indigent defense.”
A draft of the Principles and Guidelines is available here.