I want to expand on that a bit. What is the loosest definition of "natural born," as expressed by various legal scholars and politicians? "Born in the USA or territory under control of the USA."
In Congressional hearings on the eligibility of McCain, Theodore Olson and Lawrence Tribe opined that all persons born in the Panama Canal Zone would be natural born US citizens, that is, that the citizenship of the parents was irrelevant; as long as the territory was under US control.
See debate at Congressional Record, Pages S3645-3646, April 30, 2008 for a copy of the letter.
If the Panama Canal Zone was sovereign U.S. territory at the time of Senator McCain's birth, then that fact alone would make him a "natural born" citizen under the well-established principle that "natural born" citizenship includes birth within the territory and allegiance of the United States.
Notice that - NO requirement at all that either parent be a citizen, or that the child be raised with allegiance to the US. Only that the birth take place on US or US territorial soil, and under the constitution, the person reach 35 years of age and have 14 years of US residency before taking office.
And under current law, children born to illegal aliens, a mother in the country illegally, are also "natural born" citizens of the US, at least in the vernacular of statute.
I think these conclusions are in conflict with the "natural born" requirement in the constitution. That is to say, even though a person may be labeled "natural born" for immigration purposes, I do not think that person necessarily meets the constitutional "natural born" requirement for holding the office of president.
I don't think a dual citizen at birth is qualified.
I think this is where the question is going to lie and probably where the Supreme Court will have to intervene. According to the most recent statutes, even if Obama had been born in Kenya, he'd qualify as having been born a citizen of the US because of his mother's citizenship (well, under the current law, but not under the law of the year when he was born). How would the Supreme Court rule on this, especially with somebody like Sotomayor on it?
And, secondly, if the Court found for Obama, what would be the reaction of the rest of the country, knowing he qualified only on a technicality and had probably been lying about it from the start?