It's not an interpretation. It's defined in relatively simple to understand English.

U.S. Person - a natural person who is a lawful permanent resident as defined in 8 U.S.C. 1101(a)(20) or who is a protected individual as defined by 8 U.S.C. 1324b(a)(3).

Relevant portion of 8 U.S.C. 1324b(a)(3):

[A protected person] is an alien who is lawfully admitted for permanent residence, is granted the status of an alien lawfully admitted for temporary residence under section 1160(a) or 1255a(a)(1) of this title, is admitted as a refugee under section 1157 of this title, or is granted asylum under section 1158 of this title;