Originally Posted by GUWonder

The constitutional question is rather distinct from the binary of whether or not a POTUS has sole and unregulated authority to do as wished (by POTUS) when it comes to US border crossings.

For example, POTUS doesn't have sole and unregulated authority to determine which US citizens born abroad are natural-born US citizens or not. Even as that too is an authority to regulate cross-border movements. And if the Administrative exercise of making the determination of such citizenship status was done with the purpose of religious discrimination, it would still be a constitutional question beyond just the question about the authority of a President to execute in the realm of foreign affairs.