Its a bit complicated. EFF has a good post from a US perspective https://www.eff.org/deeplinks/2022/12/user-generated-content-and-fediverse-legal-primer . My understanding for US instances (and IANAL), is that if you have a TOS banning illegal content, register for a DMCA agent, and remove illegal content in a reasonably fast timeframe when you have knowledge of it, and ban repeat offenders, you should be okay.