Enemy combatant. The US courts have NO jurisdiction or say in the matter.
If you’re a US citizen, and go overseas to fight with our enemies, you become a threat to the US, and get the same treatment as any POW.
All the more reason to provide no quarter, or no prisoners.
This is the problem of dual citizens. They want the protection of the USA and the privileges of their home country. The US should not allow it.
No, ordinary POWs are entitled to certain rights. Those committing treason are entitled to an execution.