How can I access the debates of the Council and the Assembly of the League of Nations ?

The minutes of the Council are part of the League of Nations Official Journal, and the minutes of the Assembly are part of the League of Nations Official Journal, Special Supplement. The two collections are available in the national libraries, as well as in the main universities libraries. The League of Nations Official Journal is also available through the database HeinOnline (Ask your library for it): http://home.heinonline.org/