Statutory definitions can be very specific or vague, depending on the whim of the legislature. Of course, they cannot be too vague, as that can lead to their being found unconstitutional because of that vagueness. For a law to be meaningfully applied to a person, they should have some possibility of understanding that it applies to them.
Sometimes a law can be on the books for a while before a court has an opportunity to clarify exactly what it means. For instance, Iowa has a section of the statutes entitled "Dangerous Weapon."
It encompassaes, specifically "any offensive weapon, pistol, revolver, or other firearm, dagger, razor, stiletto, switchblade knife, knife having a blade exceeding five inches in length." This seems clear enough. It also includes a portable device or weapon, which produces an electric charge or pulse, "designed to immobilize a person."
It appears this statute was last amended in 2008, but this year a woman was arrested for shoplifting and happened to have a nonworking stun gun in her purse. She was charged with having a "dangerous weapon" and a judge agreed.
She appealed, and the Iowa Court of Appeals reversed on a lack of evidence. The state Supreme Court, however, disagreed and ruled that even an "inoperable" stun gun was a dangerous weapon under the statute.
A local business is now concerned because it sells stun guns for protection to women, and the owner is worried that she needs to contact all of her customers. With this interpretation of the statute, anyone without a firearm permit could be charged with an aggravated misdemeanor charge for carrying a stun gun.
She is hoping to lobby the legislature to make a change to the statute this session.
Source: qconline.com, "Iowa Supreme Court: Stun gun is a dangerous weapon," Gerold Shelton, March 5, 2016