Azamat tazhayakov reentered the country on a visa that should have been revoked. but customs and border never got the message. there's the information sharing problem we've been talking about. now effective immediately, a u.s. government official confirms that the department of homeland security is ordering border agents to confirm that every international student arriving here has a valid visa. the move is part of an effort to reform the student visa program. he's one of the friends accused of taking evidence from dzhokhar tsarnaev's room and disposing of it. also a source tells cnn investiga...