Existing US law provides plenty of means to deport people in the US illegally. Why is this executive order even necessary? I would guess that it serves two purposes: 1) gets the most bigoted Trump supporters up in arms; and 2) puts fear into the hearts of people from the affected countries, legally in the US or not. Trump is all about fomenting opinion against people who are not white and Christian or Jewish. In the case of Jewish people, his approach has backfired because much of his trailer trash support don't like Jews either!