In 1952, Congress passed something called the Immigration and Nationality Act. It has been amended dozens of times subsequently, and currently exists as a 600-page behemoth with lots of very specific rules.
Whenever the President finds that the entry of any aliens or of any class of aliens into the United States would be detrimental to the interests of the United States, he may by proclamation, and for such period as he shall deem necessary, suspend the entry of all aliens or any class of aliens as immigrants or non-immigrants, or impose on the entry of aliens any restrictions he may deem to be appropriate.
Translated from legalese: The president can ban whoever he wants, however long he wants, for whatever reason he wants.
But its not that simple, because he can not say “I want to ban Muslims from the USA.” Because that would violate the First Amendment.
SO, how does he get around this, so it will hold up in a court of law?
Nationality is not a constitutionally protected class like religion is in this country, so all he would need to do, would be say, “I want exclude anyone from Saudi Arabia, Pakistan (or wherever) from coming into this country”.
No? Check out something called “Plenary Power” doctrine.
Go ahead, Google it. I’ll wait.
For those too lazy:
..that the political branches — the legislative and the executive — have sole power to regulate all aspects of immigration as a basic attribute of sovereignty.
This basically gives the executive branch the power to regulate immigration as he sees fit for this country based on nationality.
Real simple, you have a passport from Saudi, or Iraq, or a Pakistan — sorry, no immigration into America for you.
NOW this will also ban Christians in those nations as well, something he will have to consider if he wants to ban entire nationalities from coming in the country.
What’s even easier then all of this, cut funding to the departments that process the immigration from certain countries, thus reducing staff, which reduces the amount of people able to process the entire thing, holding up things for years on end, until they give up.
God Bless America and NO ONE ELSE!