But you might cross international borders to travel to a war zone with an M4.
If you don't have a problem with that why do you have a problem with a young man exercising his rights and trying to prevent further damage and looting?
Do you have a problem with police or FBI agents crossing state lines?
I'm not sure what this has to do with the topic at hand.
... a young man exercising his rights and trying to prevent further damage and looting?
The kid would have a much stronger legal leg to stand on if he was actually defending the home or business of a family member. Otherwise, may just be a knucklehead who has spent too much time playing video games.
Do you have a problem with police or FBI agents crossing state lines?
In many cases, yes. I've said for years, in fact, that most of the crimes investigated by the FBI shouldn't even be Federal crimes.