Politician Eugene V. Debs was convicted for espionage. He had made a speech in June 1918 supporting resistance to the military drafts of WW1, and was arrested during the Palmer Raids, for violating the Espionage Act of 1917. He actually ran for President while in prison.
Editors. "U.S. Supreme Court upholds Eugene V. Debs's conviction". The Literary Encyclopedia. First published 01 March 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=12673, accessed 28 February 2015.]