Except in the case of Canada and 38 countries with a "visa waiver" status, any citizen of another country wishing to enter the U.S. is required to obtain a visa for work, education, and tourism from the U.S. Embassy in their country, as noted in this statement from the U.S. Customs and Border Protection website:
"A foreign national or alien entering the U.S. is generally required to present a passport and valid visa issued by a U.S. Consular Official, unless they are a citizen of a country eligible for the Visa Waiver Program, or are a lawful permanent resident of the U.S. or a citizen of Canada."Even in the case of those countries issuing a "visa waiver", the stay is limited to 90 days; and you must present a valid passport from your country of origin to travel into and around the United States.
In terms of shutting down visa access, the State Department's website says this:
"U.S. Embassies and Consulates are sometimes forced to limit or at times suspend visa services because of natural disasters, civil unrest, war and/or security concerns, among other reasons. The list below notes the U.S. Embassies and Consulates that currently provide limited visa services, locations where visa services are suspended, and countries that do not have embassies or consulates."So, basically, Trump isn't doing anything that hasn't been within the purview of the U.S. for years. Those who say what Trump is doing is unconstitutional or outside the law should take a good look at those existing laws. For example, if a person is a citizen of Belarus, Minsk, you can only receive a visa for the following reasons:
"Although full visa services are suspended until further notice, U.S. Embassy Minsk processes nonimmigrant visa applications for the following limited categories: A visas for diplomats and government officials; G visas for employees and representatives to international organizations; B visas for relatives of Belarusian diplomats serving at Belarusian diplomatic missions in the United States; visas for family and medical emergencies requiring urgent travel; visas for U.S. Government-sponsored travel and programs; and visas for senior citizens, 70 years of age and older. Review the U.S. Embassy Minsk website for more information. "Last I checked, Belarus is not an Arab country and not covered under Trump's ban.
Further, Section 212(f) of the 1952 Nationality and Immigration Act states this:
“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.”
Obviously the whole travel ban confusion has more to do with politics and "Trump Derangement Syndrome" than reality.
U.S. Customs and Border Protection: Entering the U.S. - Documents required for Foreign Nationals (International Travelers): https://help.cbp.gov/app/answers/detail/a_id/572/~/entering-the-u.s.---documents-required-for-foreign-nationals-(international
U.S. Department of State: Countries with Limited or No U.S. Visa Services: https://travel.state.gov/content/visas/en/general/countries-with-limited-or-no-u-s--visa-services.html
The Past Six Presidents Have All Used The Executive Power To Block Certain Classes Of Immigrants: http://dailycaller.com/2016/06/16/the-past-six-presidents-have-all-used-executive-power-to-block-certain-classes-of-immigrants/