Why was Ex Parte Milligan an important case? Question 23 options: The U.S. Supreme Court ruled that the use of military tribunals to try civilians when civil courts are operating is unconstitutional. Persons of African descent cannot be and were never intended to be citizens under the U.S. Constitution. U.S. citizens designated as enemy combatants by the executive branch have a right to challenge their detainment under the Due Process Clause. Congress has the authority to withdraw appellate jurisdiction from the Supreme Court at any time