>Barnes is wrong.
Through Article 106 of the Uniform Code of Military Justice, Congress has authorized the President to try anyone acting as a spy by a general court-martial or by a military commission, and in Article 104 has authorized trial by court-martial or military commission of "Any person who aids, or attempts to aid, the enemy with arms, ammunition, supplies, money, or other things; or without proper authority, knowingly harbors or protects or gives intelligence to, or communicates or corresponds with or holds any intercourse with the enemy, either directly or indirectly."