“How are foreign spies charged with treason?”
Good point.
They’re not charged with treason, they are charged with violations of the Espionage Act.
Treason is a difficult charge to make, the Founding Father’s purposely made it that way. They remembered the behavior of both Cromwell’s Commonwealth & “The Restored Stuart’s Bloody Assizes by the judge Lord Jeffreys - maybe the original ‘Hanging Judge’ “. So they did not want a treason charge easy to make!
The word “Treason” is thrown around on this site way too much its become our “Hitler” word.