The FBI and other agencies are often involved in raids and arrests, and actively seize websites that are supposedly used for piracy. I don't understand how you can argue that it is a civil matter that does not involve law enforcement. Just search "fbi raid bittorrent", there are plenty of examples.
Piracy historically referred to illicit printed copies created for unauthorized unlicensed material benefit to the copier, without demanded licensing terms or in absence of negotiations toward such licensing. The copyright lobby ensured it broadened to cover digital reproductions on shaky epistemological grounds imo.
