I am kind of curious how they really plan to convict this person. Maybe a weapons type charge but robbery is going to be pretty hard with an online currency. The person who traded the gold over wasn't even in the room and even Jagex has said their gold has no monetary value so he didn't actually take anything.
What would they have as evidence in a trial? A video of 2 kids and one has a BB gun. The video would not show that the kid gave him the gold and the kid didn't take the other kids cash so it looks like he pointed a BB gun at the other and walked out.
So if this kid was smart he would get a lawyer and probably walk away with a misdemeanor for the BB gun.
Bad thing about this is if the kid does somehow get away with this it will open up a whole new kind of problem. IRL trades wont be safe anymore because people will see they can get away with it. Which will basically force JAgex to turn the heat way up on RWT'ing so this doesn't end up on them.