Anyone in Mordor war-gaming Feinstein's legislation must realize it's a no-win situation for the Federal Government. The first highly publicized enforcement raids would be a rallying cry "Lexington & Concord!" to 10~30M heavily armed (albeit with small arms) and experienced hunters and veterans, who currently respect LEOs.
Pitting these two forces against each other would be travesty, a disaster, and allow common criminals to run rampant -> chaos -> anarchy. The nation-wide economic disruption/losses, property destruction, and human death toll would be staggering.