Yo-Yo,
Hypothetically, if someone was stabbing Kyle’s mother in the street and he ran back into his house, grabbed a rifle, and sent back and shot the perpetrator would he be guilty of murder because he wasn’t legally entitled to carry a gun?
If a 14 year old child was sitting in his alone in his mother’s car outside a nail salon and a man waving a knife tried to break in the car and the teen accidentally ran over and killed the attacker while trying to escape by driving away would be be guilty of the assailan’s death?
The answer to both is “not guilty” and so the answer with Kyle Rittenhouse is “not guilty!
No, he would not be guilty of murder because he wasn't legally entitled to carry a gun, and Kyle isn't guilty of murder for defending his life against those people attempting to attack him. Both examples are clear cut cases of justifiable homicide while in the defense of one's life or that of anothers.
But in your hypothetical, he would be guilty of possession of a deadly weapon if he were under 18 and didn't have a Hunter Safety certificate.