Point missed by miles. The 7 countries named in the "ban" are countries which lack the internal controls necessary for our government to conduct the necessary vetting that needs to occur before we let someone in. The governments - such as they are - in the 7 countries are known sponsors of terrorism and/or known harborers of terrorists. 9/11 hijackers came from Saudi Arabia, but the Saudi government does not sponsor terrorism. Nor do they knowingly give safe harbor to terrorists. If someone wants to come here from there, or the other 43 Muslim majority countries not named in the "ban", we can get information about them. Who is in control in Yemen? Who knows? There was a coup in 2014 and rival factions each claim control. Not getting any reliable info out of them. Information is widely available. We can't let people in if we can't even establish who they actually are.

http://www.cnn.com/2017/01/29/politics/trump-travel-ban-countries/