"It has no effect on noncitizens that are not currently IN the US."
Not completely accurate.  The Constitution applies to those under US jurisdiction, eg. applies to prisoners in Gitmo.  IIRC it also applies to those who apply for visas outside the US.  That's the PROCESS part of Due Process.  The President (or Congress) can suspend accepting applications or delay/deny granting a visa, the process is required to treat applicants equally before the law, ie. the President (and the state department) cannot violate the Constitution or fabricating reasons to deny a visa/entry, ie. "the rationale for the travel ban has to be based in facts not fiction."