A2S1C5:
No Person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President;
Justice Joseph Story, also founder of Harvard Law School, in his works of Volume 3, Section 1472-73 of ‘The Founders Constitution: Commentaries on the Constitution’ originally published in 1833 writes of the qualifications of those who wish to attain election into the executive branch as laid out in A2 S1 C5 of the constitution:
§ 1472. Considering the nature of the duties, the extent of the information, and the solid wisdom and experience required in the executive department, no one can reasonably doubt the propriety of some qualification of age. That, which has been selected, is the middle age of life, by which period the character and talents of individuals are generally known, and fully developed; and opportunities have usually been afforded for public service, and for experience in the public councils. The faculties of the mind, if they have not then attained to their highest maturity, are in full vigor, and hastening towards their ripest state. The judgment, acting upon large materials, has, by that time, attained a solid cast; and the principles, which form the character, and the integrity, which gives lustre to the virtues of life, must then, if ever, have acquired public confidence and approbation.
§ 1473. It is indispensable, too, that the president should be a natural born citizen of the United States; or a citizen at the adoption of the constitution, and for fourteen years before his election. This permission of a naturalized citizen to become president is an exception from the great fundamental policy of all governments, to exclude foreign influence from their executive councils and duties. It was doubtless introduced (for it has now become by lapse of time merely nominal, and will soon become wholly extinct) out of respect to those distinguished revolutionary patriots, who were born in a foreign land, and yet had entitled themselves to high honors in their adopted country. A positive exclusion of them from the office would have been unjust to their merits, and painful to their sensibilities. But the general propriety of the exclusion of foreigners, in common cases, will scarcely be doubted by any sound statesman. It cuts off all chances for ambitious foreigners, who might otherwise be intriguing for the office; and interposes a barrier against those corrupt interferences of foreign governments in executive elections, which have inflicted the most serious evils upon the elective monarchies of Europe.
Ben Franklin's son, who was also governor of NJ, refused to renounce England and thus was jailed charged with Treason for not relinquishing his office while continuing to adhere to the crown. Not a common story, but it should be.
“§ 1473. It is indispensable, too, that the president should be a natural born citizen of the United States; or a citizen at the adoption of the constitution, and for fourteen years before his election. This permission of a naturalized citizen to become president is an exception from the great fundamental policy of all governments, to exclude foreign influence from their executive councils and duties. It was doubtless introduced (for it has now become by lapse of time merely nominal, and will soon become wholly extinct) out of respect to those distinguished revolutionary patriots, who were born in a foreign land, and yet had entitled themselves to high honors in their adopted country.”
Which means that if Obama was born in Kenya, then he isn’t a natural-born citizen because federal law at the time only gave U.S. citizenship at birth to a child born abroad with one U.S. citizen parent if such parent had lived in the U.S. for at least 5 years after the age of 14 (and Obama’s mother hadn’t yet turned 19 years of age when he was born). However, if Obama was born in Hawaii, then he’s a U.S. citizen at birth and thus a natural-born citizen.