While much has been said about President Trump's actions on refugee resettlement and visas from seven nations in the Middle East and Africa, liberals have been remarkably quiet about the federal law that governs the President's actions.
In fact, federal judge James Robart's ruling putting a nationwide stay on those actions didn't even bother to reference this statute; in part, it would seem, because the statute is so crystal clear:
8 U.S. Code § 1182 - Inadmissible aliens
(f) Suspension of entry or imposition of restrictions by President
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 nonimmigrants, or impose on the entry of aliens any restrictions he may deem to be appropriate.
This, of course, includes a class of aliens from a specific country (i.e. any one of the seven named in the executive order) and could not possibly be clearer: President Trump has the absolute authority to issue the actions that he did.
No wonder this is most likely the first place in the media that you've seen this statute in the weeks since the executive order was issued!