Military always has an out if he showed his service papers and such before he left it would have been easier. HOWEVER if his family stayed in the US and continue to use the service after he left that doesn't give him an auto out.
If you have deployment papers they will terminate the contract without ETF like any other carrier would and are required to do.
I have done with Twice when I was in many moons ago. with Verizon and T-Mobile. AT&T and Sprint I had ended up getting once I was out. Today it's still no different.