A U.S. Customs and Border Protection officer checks the passport of a foreign visitor at McCarran International Airport in Las Vegas on Tuesday, Dec. 13, 2011. (AP Photo/Julie Jacobson)

Photo by: Julie Jacobson

A U.S. Customs and Border Protection officer checks the passport of a foreign visitor at McCarran International Airport in Las Vegas on Tuesday, Dec. 13, 2011. (AP Photo/Julie Jacobson)