As a rule, if law enforcement has a warrant then it's going to be difficult to prevent them from gaining access. You can self-host and encrypt but that's difficult for mainstream users to do, and even for experts, it limits the tools you have access to. You can also be prosecuted for refusal to decrypt a device since SCOTUS hasn't yet ruled on the scope of the 5th amendment's protections with respect to encrypted personal devices.

I think the best solution is to set content to auto-delete (unless flagged) after some period of time. You can't turn over what you don't have.