Yep. Articles of War, precursor to the UCMJ were in effect. We would have tried him.
And I do know that innumerable atrocities were commited by our own forces back then and seldom was anything ever said and few if anyone ever charged or convicted. Doesn't make them right or legal. The mechanisms to root them out just did not exist.
Hmm, Articles of War. So maybe it did happen and they covered their tracks. Or maybe Pershing somehow spread the rumor. The story originated somehow.