Upvote:3
I'm asuming you talk about a silencer for a "real" firearm and not an air gun or the like. As Calchas pointed out, national laws apply. Europe has no constitutional right to carry and bear arms, a permit is required for each weapon.
In Germany silencers require a permit similar to a firearms permit, which would be extremely hard to get since the law recognizes few legitimate uses. ISTR that pest control on cemeteries are one exception. (A sports shooter can have a legitimate use for a .45 or 9mm, but never for a silenced 9mm.)