Because the Canal Zone was a no mans land, in the words of Representative Sparkman, in 1937 Congress passed a statute, the Act of Aug. 4, 1937 (now codified at 8 U.S.C. § 1403(a)) granting citizenship to [a]ny person born in the Canal Zone on or after February 26, 1904 who had at least one U.S. citizen parent. This Act made Senator McCain a U.S. citizen before his first birthday. But again, to be a natural born citizen, one must be a citizen at the moment of birth. Since Senator McCain became a citizen in his eleventh month of life, he does not satisfy this criterion, is not a natural born citizen, and thus is not eligible to the Office of President.
Copied from here http://www.michiganlawreview.org/firstimpressions/vol107/chin.htm
Sorry, John McCain was a “citizen at birth” (NOT natural born citizen) when he was BORN because both of his parents were US citizens REGARDLESS of WHERE he was born. This law is a moot point to McCain. He doesn’t need it.