So what's the legacy? Japan lost out on including a Racial Equality clause, but in many ways they could point to 1919 and the 1920s and 1930s, as they further expanded into China and then later into Southeast Asia, of how the United States and Western powers were very hypocritical in their moral principles and international relations. It became fuel for the belief that Japan needs to liberate the rest of Asia from Western dominance, and they can point to 1919 to show how the League of Nations was founded on unjust principles.

This outdated law made the advocacy of socialist ideas and all criticism of Japan's Kokutai (National essence) illegal. The word "kokutai" vaguely referred to Japan's traditional ruling system and over the next twenty years came to be used constantly as a national unifying symbol / term so anybody seen to be speaking against or offering an alternative to Kokutai could be seen as illegal and more than 70 000 people were arrested over 20 years under this law.

On August 27, 1928, fifteen nations signed the pact at Paris. Signatories included France, the United States, the United Kingdom, Ireland, Canada, Australia, New Zealand, South Africa, India, Belgium, Poland, Czechoslovakia, Germany, Italy and Japan. Later, an additional forty-seven nations followed suit, so the pact was eventually signed by most of the established nations in the world. 

The first major test of the pact came just a few years later in 1931, when the Mukden Incident led to the Japanese invasion of Manchuria. Though Japan had signed the pact, the combination of the worldwide depression and a limited desire to go to war to preserve China prevented the League of Nations or the United States from taking any action to enforce it. Further threats to the Peace Agreement also came from fellow signatories Germany, Austria and Italy. It soon became clear that there was no way to enforce the pact or sanction those who broke it; it also never fully defined what constituted "self-defense," so there were many ways around its terms. 

In the end, the Kellogg-Briand Pact did little to prevent World War 2 or any of the conflicts that followed.