Legality of Silencers
Silencers are legal under federal law but since 1934 you must pay a $200 tax to purchase and submit to an FBI background check. Fingerprints and photos must be provided and a long wait of several months occurs before the paperwork is approved. There is no 'license' needed to own a silencer.
State law is a different matter. The following states allow ownership of silencers: AL, AR, AK, AZ, CO, CT, FL, GA, ID, IN, KY, LA, ME, MD, MS, MT, NE, ND, NV, NH, NM, NC, OH, OK, OR, PA, SC, SD, TN, TX, UT, VA, WA, WV, WI, and WY. Of the sixteen states which do not allow civilian ownership, CA, IA, KS, MA, MO, and MI allow Class-3 dealers and Class-2 manufacturers to own silencers.
Europe is much more progressive and recognizes that hearing loss is a serious issue. In Finland silencers are not regulated at all and in England and France they are available with a permit and cheap ($30 and up). With the rural areas becoming popular and with more complaints about noise pollution near shooting ranges, it is time that silencers become as unrestricted as automobile mufflers.