With recruiting techniques like this?
This young man’s experience with military recruiters started while he was still in high school. Perhaps this is one of those areas where a parental consent law might make some sense especially to those who value life. Something along the lines of:

No representative of a military organization or any other organization that trains people to kill may contact any individual below the age of 21 without written permission of the individual’s parents. No individual below the age of 21 may join or enlist in the above referenced organization without written approval of their parents.

Yes, in answer to your first questions. The above does say parents which is plural which means both parents must sign. Second, I picked 21 and not 18 as individuals in the US have been restrained from the full execution of their rights (alcohol consumption for example) until they are 21.