“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, the president 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.”
In 1979, president Carter used it to stop Iranians from entering the United States. And, he deported 15,000 of them.
This law was written in 1952. It was passed by a Democrat-controlled Congress, House and Senate, and signed by a Democrat president.