I meant legally they can't. They'd be sued and defeated in court. But not if Net Neutrality rules are undone.
If we're going to defend net neutrality, we should at least understand what we're fighting for. And it's decidedly not to allow BitTorrent traffic to make real-time protocols like VOIP unreliable. It's about not letting ISPs favor one service over its competitors. And it's about making sure that an indie developer can send traffic to internet users just as fast as Google can.
Discussions on technically-informed sites like this one should get the details of net neutrality correct.