Wrong. It's legal.
The people who should be sued, arrested and imprisoned are the anti-gun politicians, who never did research or due diligence and never made them illegal. It wouldn't have been hard to do, as even most law abiding gun owners know there is no value in them for hunting or sporting purposes. Because of that, not even the NRA could justify defending that piece of equipment. It is also an after market add on, so the NRA couldn't say they're banning the firearm itself.