When the Trump administration sought to identify persons who had come from the banned countries and engaged in terrorism, it was able to cite one sole suspect who came from Somalia and was eventually convicted of providing material support to a terrorist group. But he came to the US when he was a toddler and was convicted a decade and a half later. That’s hardly evidence of a national security crisis.
By contrast, the evidence that the ban was targeted at Muslims was overwhelming; the president openly admitted as much on the campaign trail, and pursued that purpose once in office. Indeed, no one on the court even disputed that the president had acted with anti-Muslim animus; the only real dispute was about the legal implications of that intent. The lower courts had ruled that the ban violated the Establishment Clause, which requires government to maintain strict neutrality among religions and deems invalid any government action that a “reasonable observer,” aware of all the publicly available facts, would view as intended to promote or denigrate a particular religion.
(Donald Trump listens while Supreme Court Justice Anthony Kennedy speaks during a ceremony in the Rose Garden of the White House April 10, 2017 in Washington, DC.)