I doubt that is true (by law) either.
Diplomats may get the benefit of being held to "never leave US soil, no matter where in the world they are," but they are the only exception that I can conceive of even possibly being exlcuded.
That's sound based on court cases, but pointless. The NBC clause is another part of the constitution that's been relegated to the status of "political question."
Thanks again for your insight.