No it is settled. It's the plain language of the text. Do you also think a president can redefine the 2nd amendment through an executive order?
Among countless legal tretises on the subject available on line, please see:
“Birthright Citizenship: A Fundamental Misunderstanding of the 14th Amendment”
It is “assumed” law, not “settled” law.
He can if SCOTUS goes along with it. Courts redefine and hallucinate things into being on a regular basis. The RKBA is a great example of that.