To your comment, if one is a part of the military or reserves, it doesn't automatically gives the person the right to carry in private life. Also, by your definition, one's right to arms ends at whatever the upper age limit is.
Regarding milita - YOU are the milita, therefore YOU have the right to have arms, weapons, guns...whatever to defend/fight against whatever is necessary for the country. (note: broad brush definition - one can research this themselves on the Interweb)
"With great power, there must also come great responsibility." - Stan Lee
"All that is necessary for evil to triumph is for good men to do nothing." - Edmund Burke