From my understanding, Safe Harbor Provisions in the US ensure that as long as the owner responds to DMCA requests in the allotted time, they are not liable for what users post on their sites.
Seeing as the Fediverse is way under corporate radar so far, it seems to be prudent to just wait and see what happens. Then maybe enforce a "no direct links to piracy" if needed. I don't think you can sue a site for simply referring people to sites that do have illegal content, just hosting.