Duh!

From Factcheck.org:

When Barack Obama Jr. was born on Aug. 4,1961, in Honolulu, Kenya was a British colony, still part of the United Kingdom's dwindling empire. As a Kenyan native, Barack Obama Sr. was a British subject whose citizenship status was governed by The British Nationality Act of 1948. That same act governed the status of Obama Sr.'s children:

British Nationality Act of 1948 (Part II, Section 5): Subject to the provisions of this section, a person born after the commencement of this Act shall be a citizen of the United Kingdom and Colonies by descent if his father is a citizen of the United Kingdom and Colonies at the time of the birth.

In other words, at the time of his birth, Barack Obama Jr. was both a U.S. citizen (by virtue of being born in Hawaii) and a citizen of the United Kingdom and Colonies (or the UKC) by virtue of being born to a father who was a citizen of the UKC. Obama's British citizenship was short-lived. On Dec. 12, 1963, Kenya formally gained its independence from the United Kingdom. Chapter VI, Section 87 of the Kenyan Constitution specifies that:

1. Every person who, having been born in Kenya, is on 11th December, 1963 a citizen of the United Kingdom and Colonies or a British protected person shall become a citizen of Kenya on 12th December, 1963...

2. Every person who, having been born outside Kenya, is on 11th December, 1963 a citizen of the United Kingdom and Colonies or a British protected person shall, if his father becomes, or would but for his death have become, a citizen of Kenya by virtue of subsection (1), become a citizen of Kenya on 12th December, 1963.

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.