So, is it your view that the “laws” in effect at the time he was born can narrow the constitutional qualifications?
It is my view that the laws at the time said that despite the fact that his mother was a US citizen, she was sufficiently young that giving birth to him would NOT confer "natural born citizenship" status. That law has been summarized and linked to multiple times on these threads.
The constitutional qualifications remain, but the way one can qualify for such status is modified by legislation.