Most states allow silencers. They are completely regulated by the US government. You have to get permission to own one, both from the Feds and from your local "Chief Law Enforcement Officer". And you have to pay a 200 dollar tax on each and every one you own. But you can own them in MOST places.
Many people on the forums are not in the US (it is the WORLD-wide web, after all), and in just about every other country in the world silencers are not only legal, but the mark of a polite shooter, Just like you wouldn't run your lawn mower without a muffler, or drive your car without a muffler, you don't shoot your gun without a muffler. Shooting an unmuffled gun annoys the neighbors and scares the animals.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.