Perhaps you're not familiar with U.S.C. 1385, aka Posse Comitatus Act. It specifically prohibits the use of our military in domestic policies. That's why our troops are limited to support operations.
First, my understanding of Posse Comitatus Act is that the US military cannot be used against US citizens. These are not US citizens. By your definition we would NEVER be able to use the US military to protect our domestic border?
Secondly, my response was regarding the poster who said we our military could not be ready to protect our border within 3 weeks. Again, that seems absurd considering what if we were attacked by a foreign government - we would not be able to protect our border for 3 weeks? That doesn't make sense to me.