Nope, try again, A US Citizen has an absolute right to re-enter the US. Lyttle v US, Fikre v FBI, and other cases uphold this. They can detain you, they can make life difficult, but if you're a US citizen, they *cannot* send you back.
Can't they send the US citizen to another part of the world that is under US jurisdiction, like Guantanamo bay? Or some military facility? That way you have been allowed to re-enter the US, just a part of the US where they can then control your movements.