So the Ninth Circuit held today (Teter v. Lopez), in an opinion by Judge Carlos Bea, joined by Judges Daniel Collins and Kenneth Lee.
The butterfly knife, also known as the "balisong," has a disputed origin. Some sources say it originated in France; others, the Philippines. It is anywhere from a few hundred to over a thousand years old. Regardless of its origin, the butterfly knife resembles an ordinary pocketknife, a tool that has been used by Americans since the early 18th century (at the very latest). See State v. Delgado (Or. 1984). Like a pocketknife, the butterfly knife comprises a handle and a folding blade, the cutting edge of which becomes covered by the handle when closed. Unlike a pocketknife, however, the butterfly knife's handle is split into two components. Together, these two components fully encase the blade when closed and rotate in opposite directions to open. With a few short, quick movements, an experienced user can open a butterfly knife with one hand….
