system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are Brass Knuckles and Blackjacks illegal, but not other weapons? I know they are concealed weapons, but then there's knives and guns.
gpt
Because of their unique history as weapons associated with organized crime. There are not illegal in every state, but are almost always in states with particularly brutal Mob histories.

Note, sawed-off shotguns are banned for the same reason.