The Constitutional discussion is necessary, but there is a U.S.C. Title Code on the matter, as well.
It was a topic of discussion within the last 30 days on FR.
Do you mean this...
8 USC CHAPTER 12, SUBCHAPTER III: NATIONALITY AND NATURALIZATION, Part INationality at Birth and Collective Naturalization
§1401. Nationals and citizens of United States at birth
The following shall be nationals and citizens of the United States at birth:
(a) a person born in the United States, and subject to the jurisdiction thereof;