[dragonwriter]

It’s not citizenship (otherwise asylees, refugees, and even permanent resident aliens would be excluded.)

A “foreign person” is defined in ITAR (22 CFR Sec. 120.63), by reference to two sections of immigration law in Title 8 of the US Code, as someone who is none of the following: a US citizen, a lawful permanent resident, an asylee or refugee, a person lawfully admitted for permanent residency (I haven’t done the analysis to see if this is distinct from “lawful permanent resident” or if its overlap with different language between the categories referenced from different parts of Title 8 of the US Code), a person lawfully admitted for certain classes of temporary residency.