You said there was no law and I provided the link to one. Whether or not it is Constitutional is up for the courts to decide. And if the President issues his Executive Order then challenges to that will give the courts the case they need to weigh in on the question and decide it once and for all.
The law you cited does not say that children born to foreign nationals on U.S. soil become U.S. citizens.
Foreign nationals are subject to the jurisdictions of their own countries. Not ours.