Switch blades are nothing more than a specifically engineered tool. The idea behind switchblade knives is to allow a person with only one functional hand to be able to use a knife. Also addresses the need of individuals with disabilities of the hand and fingers(insufficient grip strength). I did some research a few years ago and they are legal for persons with said afflictions and Law Enforcement personnel.
There are varying mechanisms for opening, some will open as a folder with a spring assist while others will spring straight out from the hilt. I have models of both but do not like to carry due to the possibility of an inadvertant opening when in a precarious position like a front pocket
And yes I do own mine legally.