If you are looking for documents published by the League of Nations, then our colleagues in Official Papers (on the ground floor of the Law Bod) will be happy to help. They have written the special guide, below, as a beginning
Office Without Power : Secretary-General Sir Eric Drummond, 1919-1933 by 
Peace Through Law: Britain and the International Court in the 1920s by 
International Legal Argument in the Permanent Court of International Justice by Globalization of labour rights
ILO Histories : essays on the International Labour Organization and its impact on the world during the twentieth century by 
The Ottoman endgame : war, revolution and the making of the modern Middle East, 1908-1923 by Leipzig (war crime) Trials of 1921
The Trial of the Kaiser by and the concept of genocide see the relevant pages in the Guide below