It was the Washington Post reporter he supposedly showed it to.
http://www.law.cornell.edu/uscode/8/1403.html
“Persons born in the Canal Zone or Republic of Panama on or after February 26, 1904
(a) Any person born in the Canal Zone on or after February 26, 1904, and whether before or after the effective date of this chapter, whose father or mother or both at the time of the birth of such person was or is a citizen of the United States, is declared to be a citizen of the United States.
(b) Any person born in the Republic of Panama on or after February 26, 1904, and whether before or after the effective date of this chapter, whose father or mother or both at the time of the birth of such person was or is a citizen of the United States employed by the Government of the United States or by the Panama Railroad Company, or its successor in title, is declared to be a citizen of the United States”
That law only grants citizenship, not NBC. So, playing along with whichever story of McCain being born somewhere in Panama and his father being stationed there, he’d be a US citizen but still not eligible for POTUS.
Thanks for the info and link.