The travel ban is based upon the same legal principal, ie. deference to the Executive.  In the Korematsu case, the Supreme Court (which has never reversed the decision but I believe every Justice that was on the Court came out and said it was a bad decision afterwards) agreed with the administration lawyers that involuntary imprisonment/internment simple because of the potential for betrayal/harm.  The Court deferred to the judgment of FDR's administration.
While there are some differences, in this case we are not in a state of total war, the same basis of fear of betrayal/harm is unfounded.  Trump's claim that the travel ban is necessary to establish "extreme vetting" has never been supported by anything but the simple claim "the Court should defer to the President."