Isn’t a Military Tribunal a separate thing from the Federal Justice system?
No it is a Federal court that operates under the Manual for Courts-Martial. Its procedures differ and the rules of evidence are such that the 'all' evidence can be considered as long as it is germane to the case. All capital cases are subject to an automatic 30 day review.
Tribunals are still considered inferior to the Supreme Court.
This is a nice summary on how the Constitution covers them:
Article I, Section 8: Authorizes Congress to establish tribunals inferior to the Supreme Court, including military tribunals.
Article II, Section 2: Designates the President as Commander in Chief, providing a basis for military tribunal use.
Article III, Section 1: Establishes judicial power, distinguishing civilian courts from military tribunals.
Fifth Amendment: Provides an exception for military matters, allowing actions without grand jury indictment in specific cases.
Key cases:
Ex parte Milligan (1866): Established that military tribunals cannot try civilians when civilian courts are available.
Ex parte Quirin (1942): Upheld the trial of German saboteurs by military tribunal, distinguishing it from Milligan.
Hamdi v. Rumsfeld (2004): Addressed detention of American citizens as enemy combatants, emphasizing due process rights.
Hamdan v. Rumsfeld (2006): Required military tribunals to comply with the Uniform Code of Military Justice and Geneva Conventions.