You can own a foam filled suppressor. Its legal. Its illegal for a USA based company or distributor to sell to minor or private collector. The reason its legal is because the threading is such that its impossible to mount to any real firearm with the exception of an AK47(positive threading) The ATF would also have to prove with a commercial airsoft suppressor that the foam absorbs the expanding gas from the round as it leaves the barrel. This is impossible because airsoft suppressors dont have a baffle system. If you want to believe the "geniuses" at KWA over me; please contact your local BATF office and repeat the legality of airsoft suppressors back to them. Dont feel insulted if they laugh before hanging up on you.