Just pasted this from a good source for your info:
Contrary to popular belief, silencers are and always have been legal to own under federal law. There are, however, 16 states, plus the District of Columbia that prohibit the civilian ownership of silencers. At this time, the following states allow private ownership of silencers: AL, AR, AK, AZ, CO, CT, FL, GA, ID, IN, KY, LA, ME, MD, MS, MT, NE, NV, NH, NM, NC, OH, OK, OR, PA, SC, SD, TN, TX, UT, VA, WA, WI, and WY. Of the fifteen states that do not allow civilian ownership, CA, IA, KS, MA, MO, and MI allow Class 3 dealers and Class two manufacturers to possess silencers.
To legally purchase a silencer or any item falling under the purview of the NFA, you must be at least 21 years of age, a resident of the United States, and have no felony record. The first step is to locate a Class 3 dealer in your state who either has or will order the item you are interested in. Once a product and price have been settled on, the Class 3 dealer will provide the prospective purchaser with duplicate ATF Form 4's and two sets of fingerprint cards. The Form 4's must be filled out on both sides, with passport photos of the prospective buyer affixed to the backside of the form. The buyer then has the Chief Law-Enforcement officer* sign the rear of the Form 4's attesting the prospective purchaser does not possess a criminal record and is not wanted. The two fingerprint cards must be completed and signed by a Law Enforcement agency. The completed paperwork is then sent to the Department of the Treasury with a check or money order for $200.00. The $200.00 is known as a "transfer tax" because as it must be paid whenever ownership of the silencer is "transferred" (in this case, the dealer to the prospective purchaser). As long as ownership remains with the same person, the tax need not be paid again. Only if the owner sells it will a new transfer tax need to be paid. An owner may will his silencer to a lawful heir with no tax incurred.
Once the paper work is submitted, it normally takes 60 to 120 days to receive the approved, stamped paperwork from NFA Branch. It is only upon the return of the approved paperwork that the dealer can allow the prospective purchaser to take possession of their new silencer. A copy of the approved paperwork must accompany the silencer at all times (the original should be stored in a safe deposit box). Silencers can be transported to other states that allow their ownership, but to transport a silencer into one of the sixteen states which prohibit private ownership can subject the owner to serious state felony charges.
*The following is a list of typically encountered Chief Law Enforcement Officers (CLEO):
* Chief of Police
* Head of State Police Agency
* District Attorney
* A judge with the power of arrest
* Any other law enforcement officer approved for this procedure by the National Firearms Act branch of the BATF.