HeinOnline: History of International Law includes materials dating back to 1690 on the history of international law and includes subjects such as war and peace, The Hague Peace Conferences and Conventions, the Nuremberg Trials, law of the sea and international arbitration.
Some interesting items in this database are: Aerial Warfare in International Law, Crimes against International Law, Cases of International Law during the Chino-Japanese War, Aviation in Colombia, Chile and Brazil , Enemy Prisoners of War, American-Brazilian Private International Law, American-Chilean Private International Law, Briand-Kellogg Pact of Paris, Diplomatic Commentaries, Essays on Espionage & International Law, Alabama Arbitration, The International Labour Organization - The First Decade, The Spanish origin of International Law, Turkey in the World War’ and much more.
This database also contains documents in French, Spanish and German. Start your research here.