When it was ascertained that a state of war existed between Italy and Ethiopia, I performed the duty imposed upon me by legislation, by issuing proclamations making effective an embargo on arms, ammunition and implements of war from the United States to the belligerent countries and admonishing American citizens to abstain from traveling on belligerent vessels.
In doing so, I was standing upon a question of fact. Having now ascertained that, in fact, the conditions which led to the issuing of the proclamations have ceased to exist, I have, in conformity with the duty imposed upon me, issued proclamations revoking my earlier proclamations.
Therefore, the statements which I issued in respect to commercial transactions with the belligerents are no longer applicable.
Franklin D. Roosevelt, Statement Revocing Neutrality Proclamations in War between Italy and Ethiopia Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/208898