Revoke their citizenship?

Some Congresscritter from Georgia thinks it would be a good idea to strip US citizenship from turncoats like John Walker Lindh.
I agree. But I think it should be stripped from them by lethal injection, or gas chamber, or electrocution, or hanging, or being shot in the back of the head with a large-calibre pistol. Not by some obscure law that will probably be honored more in the breach than in the observance (like the Logan Act).
The penalty for betraying your fellow citizens should be DEATH. What part of this do our representatives, senators, Presidents, and judges not understand?