I mean under the laws then in effect Obama’s mother was too young to pass on citizenship, so there only remains the fact that Obama was born in the one of the United States, to a mother too young to pass on citizenship, and a father who was a foreign national. The statement, "too young to pass on citizenship" ONLY applies to a US citizen parent married to an alien, and to a child born outside the US. It does not apply to those born in the US. If born in the US, a child with such parents is a citizen at birth, but not a natural born citizen, since they still would only have one citizen parent.
Here is the entire paragraph:
The U.S. law in effect during Obama’s birth stated if you are born abroad to one U.S. parent and a foreign national, the U.S. parent must have resided in the United States for a least 10 years, five of which were after the age of 14 in order to register the child’s birth abroad in the United States as a “natural born” U.S. citizen. (Nationality Act of 1940, revised June 1952 and affirmed several times since). Since Obama was born in Hawaii, this law does not directly apply to him. It does, however, offer another specific definition of “natural-born” citizenship - one which confers “natural-born” status to multi-national children insofar as the US parent has resided in America for 10 years, five of which occur after the age of 14. Unfortunately, Obama’s American mother was just 18 when she delivered him. So he fails to meet even this definition of “natural-born.”