Please to explain...

I was reading about the case of Amelia S., a 17-year old girl from Indiana with clinical depression who fled National Guard boot camp without authorization and returned home. The Guard tried to force her back to training, in defiance of rules regarding people with diagnosed mental disorders. She has now been released due to public pressure, despite the handicap of being forbidden to retain counsel for her own defense due to her age. (Unfortunately, the website for the Catholic Peace Fellowship, where I’ve been following the story, does not seem to have the older posts on Amelia S. archived.)

Which leads to my question. In general, minors have various restrictions on what they can do and the kind of commitments they can undertake. Which leads me to wonder, how in God’s name is it legal for a 17-year old to enlist in the military, even with parental consent? She’s not old enough to legally buy alcohol, smoke, have sex with an adult in some states, buy a gun, or gamble. American law does not consider her mature enough to give meaningful consent to these things, nor to deal with the consequences and responsibilities they entail.

In the eyes of the law, however, she is fully competent to enter a binding contract- one which has criminal penalties for breaking it, no less- committing her to several years of employment in a job that poses a significant risk of death or permanent disability. Could somebody explain how, exactly, that makes sense? Because I keep trying to imagine a universe where this is even remotely sane, and I’ve started to bleed from the eyeballs.