It says:

"Manufacture, possess for sale, sell, or furnish to any person other than a law
enforcement agency for authorized use in police work, any brass knuckles, cestus, billy, blackjack, sandbag, switchblade knife, springblade knife, gravity knife, or similar weapon;"

Specifically, possess for sale, sell, or furnish to...

It doesn't really say it's illegal to possess one for personal use.