If it isn't registered with the BATF with the $200 tax stamp, 10 fingerprints, photo, anal probe, and background check, it's a felony to possess. It's even a felony to possess the *parts* for a silencer, though the BATF has to prove you intended to make a silencer from the parts to a jury. (Which they have done in the past.)
This law is federal - it applies everywhere.