Pros & Cons:
If you leave the USA and join a terrorist group should your Constitutional rights be voided?
My opinion is if you have openly given up you citizenship in writing or though a public forum, then I think you are no longer a citizen. If you have not, then you are still a citizen and are entitled to your rights, but should be tried for treason. If the facts warrant your guilt, you should be hanged as a traitor. If you are close to other enemies and you are killed, that is part of war.
To single you out as a target when you are a citizen is a slippery slope to freedoms being removed. What can be taken away next?