You are right. The constitutional rights in these cases are those of citizens or legal residents. For example, if I am a citizen or a legal resident and a Muslim the ban may intrude on my rights because I cannot bring in my wife because of religious reasons or lack of procedures— due process— for her to join me because the ban is absolute— even if she is a Christian or we are both Christians.  Much of the constitutional argument focused on whether there was a non-religous reason for banning people from the six countries and no other countries . The first ban was badly written because it seemed directed against Muslims and not terrorists and many countries producing terrroists were not included in the ban.