YES, SILENCERS ARE LEGAL

 AND THEY ARE EASY TO OBTAIN THROUGH PROPER CHANNELS.
No, you do not need a license to purchase a silencer, but you do have to pay a one-time $200 tax for each silencer you purchase. You also must:

BE AT LEAST 21 YEARS OF AGE TO PURCHASE A SILENCER FROM A DEALER

BE AT LEAST 18 YEARS OF AGE TO PURCHASE A SILENCER FROM AN INDIVIDUAL ON A FORM 4 TO FORM 4 TRANSFER (CONTINGENT ON STATE LAWS)

BE AT LEAST 18 YEARS OF AGE TO POSSESS A SILENCER AS A BENEFICIARY OF A TRUST OR AS A MEMBER OF A CORPORATION

BE A RESIDENT OF THE UNITED STATES

BE LEGALLY ELIGIBLE TO PURCHASE A FIREARM

PASS A BATFE BACKGROUND CHECK WITH A TYPICAL PROCESS TIME OF 180 DAYS
RESIDE IN ONE OF THE 41 STATES THAT CURRENTLY ALLOW CIVILIAN OWNERSHIP OF SILENCERS

DETERMINE WHETHER OR NOT YOUR STATE ALLOWS SILENCER OWNERSHIP
Silencers are legal but are regulated by federal law and on a state-by-state basis. The National Firearms Act (NFA) branch of the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) ultimately controls any transfers; this branch registers all silencers. Individuals, corporations, and trusts can legally purchase and possess silencers in 41 states. However, if you are an FFL dealer, manufacturer, peace officer, or member of a law enforcement agency or other government agency, there are additional states where you can own a silencer. Look at the map to see if you are eligible.

 
Please visit this link for more detailed information on ownership and history of suppressors.
(link will take you to a different website)