Title 18 Section 1385. Use of Army and Air Force as posse comitatusWhoever, except in cases and under circumstances expressly authorized by the Constitution or Act of Congress, willfully uses any part of the Army or the Air Force as a posse comitatus or otherwise to execute the laws shall be fined under this title or imprisoned not more than two years, or both.
In fact, wouldn't this act specifically FORBID the use of military tribunals to "execute the laws?"
Only if you consider foreign nationals charged with terrorism and part of the network that we are at war with, civilian criminals. Bush’s EO expressly targets members or supporters of Al Qada(sic). It also expressly defines Non-Citizens as subject to these tribunals.