Come to think about, the weapon would be classified in California as a blackjack, billy, billy club, or billy jack. They are typically leather with a weighted device inside. They are very much illegal in California and most (or all) other states. Check your laws.

It does look cool, but there are a lot of cool weapons I can't carry because of laws, unfortunately.

I don't think the device is a "loaded fist", unless you grab the ball and punched with the ball in your fist. This weapon doesn't appear to be intended for that purpose.