I would like to post this again for everyone.  The president’s authority to declare such suspensions can been found in section 212(f) of the Immigration and Nationality Act, the pertinent part of which reads as follows:  “(f) 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.”