People attain U.S. citizenship in 3 ways:
- at birth by location (Jus soli - like Keith being born in the U.S.);
- at birth by blood (Jus sanguinis - like John McCain being born in Panama to U.S. citizen parents); or
- by naturalization through immigration services (like Chemda).
If Wikipedia is to be believed, Joe Francis was born in Atlanta and grew up in the U.S., therefore his twin daughters were naturally born U.S. citizens by blood. The current law says that a U.S. citizen parent that lived in the U.S. for five years, two of which were after the age of 14, transmits citizenship at birth to their child. Joe has at least five years of footage of himself over age 14 in bars with drunk women, so he can easily prove that.
Two of my three kids were born in Ukraine, but both are naturally born citizens because I lived in the U.S. until I was 20, and I could show 4 years of high school and 2 years of college transcripts to prove I was present 6 years in the U.S., at least two of which were after age 14. So, despite being born outside U.S. territory, my children can be U.S. Presidents.
This law is also the reason I can't stand the "birther" argument against Obama. If Obama had been born after November 29 instead of August 6, 1961, there would be no debate. Obama's mother was born August 29, 1942, and Obama was born on August 6, 1961, when his mother was 18 years, 9 months, and three weeks old. Under the current law, even if Obama was born in Kenya, he still would have been a naturally born U.S. citizen. The law at the time was that you had to live 10 years in the U.S., five after age 14, to pass citizenship to children. At the time, Obama's mother missed that mark only by 2.25 months.