Earlier quoted context omitted.
I'm not a US citizen so I'm just commenting as an observer. I'm a lot less worried about legislation overall because it does get scrutinized by the wider elected legislature. At the end of the day if the US as a nation decides to restrict immigration more then that's your prerogative as a nation. The American people voted in Trump and the current largely Republican legislature fair and square and they do have a right…
US immigration law gives the president explicit right to do exactly what he did (and that has been upheld by the supreme court in the past). See section f https://www.law.cornell.edu/uscode/text/8/1182
Clearly the federal courts (six different district courts, if I've counted correctly) don't believe that the case is as open and shut as you do, or they wouldn't have aisued restraining orders against the EO, one of the explicit considerationa for which is likelihood of prevailing on the merits.
That one section of law appears to be a broad grant of power does not mean that that grant is not constrained by other provisions of law.