They won't let you in. They'll just put you on a flight back.
Sometimes, they won't even let you board. See this latest example: http://www.latimes.com/news/nationworld/nation/la-na-0629-no...
Sometimes, they won't even let you board. See this latest example: http://www.latimes.com/news/nationworld/nation/la-na-0629-no...
http://knifetricks.blogspot.com/2010/09/10-brief-responses-t...