The United States Constitution requires that Presidents (and Vice Presidents too) of the United States be “natural born citizens” of the United States. However, the Constitution does not define what is a “natural born citizen.” (See Obama a ‘Natural Born Citizen?’.)
No one seems to dispute that a child of American citizens born on the soil of the United States is eligible to hold the office of President upon reaching the required age. And everyone seems to agree that a person naturalized as a U.S. citizens is disqualified from holding that office.
However, what about someone like John McCain, who although born of American citizens, was not born on American soil. Or what about Barack Obama, whose birth record shows him born on United States soil of a foreign national who was temporarily in the United States on a visa? Do either one of them qualify for the Presidency under the U.S. Constitution?
No one knows the answer to that question, as the Constitution does not tell us.