Why is a ballistic knife illegal?

A ballistic knife is illegal in many places because it launches its blade as a projectile. Lawmakers treated that design as a concealed weapon with higher assault potential than an ordinary knife because the blade can travel several feet after firing. In the US, federal law specifically restricts ballistic knives, and some states ban possession as well. The core legal issue is not blade length alone. The launch mechanism triggers the restriction. Legislatures grouped ballistic knives with weapons designed for rapid surprise attacks rather than normal cutting work. That is why a standard fixed blade may be legal in a place where a ballistic knife is not.