"The president's order is intended to protect the homeland and he has the constitutional authority and responsibility to protect the American people."
Then if that's the case he needs to halt immigration from countries where people have actually killed Americans - of the seven countries he's singled out, not one person has killed an American in an act of domestic terrorism in the past 40 years.  Banning travel from Saudi Arabia makes more sense.  but of course Trump has real estate investments there.