It seems analogous to air guns, which use compressed air to expel a projectile. Yes, the ATF says "welp, not a firearm". About half of US states have some kin

It seems analogous to air guns, which use compressed air to expel a projectile. Yes, the ATF says "welp, not a firearm". About half of US states have some kind of explicit regulations though... [1] https://en.wikipedia.org/wiki/Air_gun_laws#United_States https://en.wikipedia.org/wiki/Air_gun_laws#United_States