Fortunately for the rest of us, they can't legislate reality. They take down Napster, it goes fully distributed. They flood the networks with shit, torrent sites provide ratings. They go after TPBs trackers, we get magnet links. They start blocking at ISP level, torrents go encrypted. And sometimes they run into setbacks, they couldn't shut down the Bittorrent protocol. They haven't been able to shut down file lockers. Their mass lawsuits/shakedowns have largely been halted. VPNs and open Wifi is still legal. And when they do score a win like being able to shut down a site, a zillion mirrors and proxies pop up making it futile.
The war on piracy hasn't exactly had the same kind of popular appeal as the war on drugs. It is a lot easier to come up with horror stories about crack whores and heroin addicts than about people pirating MP3s. I'm guessing this is the main reason we haven't seen haven't seen bigger legal opposition is the fact that offense is the best defense, so far the easiest solution has been to come up with a better tool. If they manage to get rapid-fire site take downs in the DNS system, there's also the dark web solution. The TOR system isn't built for heavy P2P, but just for getting magnet links - which is the only thing you need to bootstrap the process - it's plenty. So from where I'm standing they might get bigger and bigger guns, but the target is getting harder and harder to hit in the first place and punch through the armor if you do.