When the story about the teen girls from Colorado who were going to Syria to join IS but were intercepted in Germany and returned home came out (
http://www.cnn.com/2014/10/22/us/col...sey/index.html), I thought that perhaps we should have let them.
Let 'em know that they will be branded as terrorists, never allowed to return home, and the government would do all that it could to kill them. If they are OK with that, then let 'em go. Why keep them here where they can potentially do a lot more damage? Of course, one possible answer to that is so that they can be monitored by the FBI which might lead to identification of other conspirators.