Vic Mensa was caught riding dirty in California, but you can forgive him if he didn't know he was.

Earlier this month, cops in Glendale pulled Mensa's motorcycle over for making an unsafe turn.  They found a pair of brass knuckles in his back pocket and charged him for felony possession of brass knuckles.  He was arrested and released on a 20K bond.

Fist-load weapons are a no-no in Cali but are legal in other parts of the country.

As for why Mensa was riding around with brass knuckles  ... given his punk rock aesthetic, they were just as likely a fashion accessory as they were a means of self-defense.