The correct term is "Suppressor".
I'm in CA, so I may not have this exactly right, but as far as I know, you pay a fee/tax and you can legally buy a suppressor. Otherwise they are illegal to possess.
“If ye love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you, and may posterity forget that ye were our countrymen.” ― Samuel Adams