"Since Sen. Obama has neither renounced his U.S. citizenship nor sworn an oath of allegiance to Kenya, his Kenyan citizenship automatically expired on Aug. 4,1982.
http://fightthesmears.com/articles/5/birthcertificate
Because he had a Kenyan father.
I had no idea — what’s up with that? If he was a Kenyan citizen then he wasn’t a native born American citizen?