So give these folks their due process and accuse and try them for treason. If
they don't show up to defend themselves, try them in
absentia
.

Then if they are convicted, revoke their
citizenship.


I would go one step further. If they are convicted of a capital crime, sentence them also.

What is the punishment for a capital crime? Death, right?



Conservatism is a pale horse, and the riders should be called DEATH.