Weapons are commonly distributed items used by all Occupations and their Titles. The legality of weaponry is decided by the World Government. Normal Weapons such as Swords and Guns are non restricted and are commonly bought and sold. Other weaponry such as supernatural devices like Dials are restricted to whom the Government allows. While Rare Weapons such as Wazamono Grade Katana's are also unrestricted and sellable despite their dangerous capabilities.
Most Weapons are bought and sold on the market and are completely legal, which don't require registration. While Supernatural Weapons and Grade Katana's must be either registered or found on adventures. When this occurs they are normally counted for by the Govt and registered accordingly.