With thanks to Eleanor for the link to this excellent video…

In 1928, in Paris France, accompanied by a grand ceremony, a treaty was signed by more than 60 nations to renounce war as a political instrument in international controversies. The United States also signed this treaty. This treaty is known as the Kellogg-Briand Pact. And apparently it is still valid. It is not formally renounced, repealed or withdrawn by any signatory, just ignored and more or less forgotten. War in all it's form is by the definition of this pact illegal, even the defensive or 'preemptive' ones. This pact was really meant to eliminate war by setting up a body of laws and a world court to deal with war as a crime. The prosecution of the Nazi's under the laws of this pact was ironic because ALL countries involved in the second world war were breaking these laws.

EagleEyes