Actually they did it here in Title 8 > Chapter 12 > Subchapter III > Part I > § 1401 thru § 1409 of the U.S. Code.
Pay special attention to where they define who is a citizen at birth.
A birth certificate must include your full name, the full name of your parent(s), date and place of birth, sex, date the birth record was filed, and the seal or other certification of the official custodian of such records.