Yea, those pesky immigration laws are to blame. Mean while:
http://www.theamericanconservative.com/articles/afghan-soldiers-went-awol-in-america-for-years/

"The news that 152 Afghan soldiers who came to the U.S. for training went AWOL generated a bit of excitement this month—especially since 83 of them never returned and several are considered “high risk” by federal officials because of their age and military training."