According to Prof. Gabriel J. Chin, John McCain was un-American for the first year of his life.
At the time of Mr. McCain’s birth, the relevant law granted citizenship to any child born to an American parent “out of the limits and jurisdiction of the United States.” Professor Chin said the term “limits and jurisdiction” left a crucial gap. The Canal Zone was beyond the limits of the United States but not beyond its jurisdiction, and thus the law did not apply to Mr. McCain.(Previously)
In 1937, Congress addressed the problem, enacting a law that granted citizenship to people born in the Canal Zone after 1904. That made Mr. McCain a citizen, but not one who was naturally born, Professor Chin said, because the citizenship was conferred after his birth. [Link]