Chapter 13 of the U. S. Code
§ 311. Militia: composition and classes
The militia of the United States consists of all able-bodied males at least 17 years of age and
2nd Amendment excerpt:
" A well regulated militia being necessary to the security of a free State"
So if we had some fantastic emergency we could see 17 year olds called up for militia duty with the posssibility of being trained and armed by our government. I wonder if this was the case in our early years before we became a a nation and after we became a nation. IN our early days I bet children were taught to shoot for hunting and defense purposes. on the frontier.
You can enlist in the United States Military at age 17 with your parents permission. You can enlist at the age of 18 without you parents permission.
My thoughts are on the matter if you are able to give you life for you country at the age of 18 then you should be able to enjoy the fruits of that liberty. If you enter the military and graduate from Basic Training and AIT you have shown some discipline and responsibility.
If anything an exemption should be made for military personnel under the age of 21.