Also from Scotusblog:

Justice Kennedy’s concurrence says, essentially, that there are some things that are unconstitutional that the Judiciary is not in a place to correct or address. It’s subtext is pretty close to the surface, and seems designed to chastise the Executive while agreeing with the majority that there was not anything the Court could do about it.

Again, the Constitution needs to be updated. When it was written, the founders could not have foreseen a time when modern travel and technology would raise these issues.