If he was born in Hawaii then he's a natural-born citizen per the 14th Amendment and federal law. Both state that children born in the U.S. are citizens from the moment of birth. Since the Constitution identifies only two forms of citizenship - natural born and naturalized - then if you are not one you are the other. Clearly people born in the U.S. are not naturalized citizens so they are natural- born.
“Sole U.S. jurisdiction was a core requirement for 14th Amendment citizenship. The 14th Amendment granted citizenship to emancipated slaves and their descendants, because they were, and have always been, under sole U.S. jurisdiction.
“For sake of argument, if the 14th Amendment had redefined “natural born citizen” to mean anyone “born in the U.S. and subject to the jurisdiction thereof” (where “jurisdiction” is understood to mean sole U.S. jurisdiction), Obama would still fail to meet the natural born citizen requirement. Here’s why...
“On his web site, Obama claims that his father was a British subject and that, in 1961, the citizenship status of children of British subjects was “governed” (that’s Obama’s word) by the British Nationality Act of 1948. Thus Obama’s citizenship status, at birth, was “governed” by British law, in addition to U.S. law.
“If Obama’s citizenship status at birth was “governed” by the laws of a foreign country, how could he, at birth, be subject to sole U.S. jurisdiction, which is an essential requirement for 14th Amendment citizenship? “
http://people.mags.net/tonchen/birthers.htm#ref08