I know Wisconsin has some of the most permissive knife laws. One of the core foundations within WI knife laws is: "If anything shall be called a 'dangerous weapon', it shall not be a knife." But there are exceptions: "If a defendant has/had been adjudicated to a state asylum for the legally insane, he may not carry a knife or dangerous weapon during the commission of a serious crime, or be found roaming about in possession of the same.
If anyone is disqualified from obtaining a permit to carry a concealed weapon by his local law enforcement agency, for reason of 'officially documented' mental defect ***(I think this means that local law enforcement personnel may deem a person to have a mental defect, but that determination alone is not legally binding as having a mental defect)***, he may not roam about in possession of a knife or dangerous weapons.
Then there a few other exceptions, such as carrying machetes, swords, and knives designed for no other use than mayhem or homicide. ***(The lawyer commentary noted 'it is difficult to imagine such a knife', but there is presently no case law precedent)***
Switchblades are not considered distinct from manual opening folders. All this was accomplished in one of the most restrictive states on knife rights when the State Assembly was addressed several times by historical knife-law experts who convinced enough legislators that knives are the most ancient and most useful 'tool'. Only recently have laws ignored that fact. Also, in 98% of all homicides, only hands and feet are used to effect the crime. Also, up until 1964, New York City 7th graders on up carried their rifles to school, for marsmanship class. And, until 1981, Cub Scouts and Boy Scouts carried folding knives in elementary school.
Neither of those practices had even one documented case of violence associated with it. However, it is still illegal to sell or supply (except parents and/or guardians) edged knives to minors, or for minors to roam about unsupervised in possession of a knife.
When I'm visiting my relatives in northern WI, who mostly live on farms, I carry a 10-inch knife with 7-inch fixed blade on my belt, even in town at the taverns. No one even takes notice. It's pretty common to carry fixed-blade edcs in that area. But on Sunday, no one has anything but a small folder with him.
And, up there, no one pulls a knife in a bar fight. One day the state legislature voted, and the following day anyone could carry a switchblade.