Personally I think the biggest hurdle will be moderation and defederation as it pertains to the first amendment. I believe there was already a supreme Court case where blocking a user on Twitter (from an official govt account) was deemed unconstitutional. This precedent might mean a govt instance is not allowed to defederate with any other server unless they defederate with all(?) This is pure speculation on my part, but I can guarantee it would go to the courts.