Military tribunals were used (& abused) occasionally in early US history, particularly during the Civil War.
britannica.com/event/Ex-Parte…
slate.com/news-and-polit…
oyez.org/cases/2003/03-…
oyez.org/cases/2003/03-…
oyez.org/cases/2005/05-…
oyez.org/cases/2007/06-…
libertyproject.com/overturn-a-sup…
federalregister.gov/documents/2018…
c-span.org/video/?c474730…