They might be able to go after them on stalking charges. However, it's often faster and easier to go straight to the site owners or web hosts, whose terms of service often have looser definitions of stalking, harassment, and violation of privacy.

As for letting folks know about problematic authors, some folks on GR have shelves with names like attacks-authors. There's also a more public list somewhere on GR--I ran across it while surfing links on this wank.