@jwildeboer @serapath I don't think this is possible with ActivityPub.
It might work with a much more centralized design, and with some very heavy cryptographic intervention. But even then, I'm not sure.
All protocols are extensible. Good protocols include a structured mechanism for extensibility; bad ones don't.
@jwildeboer @serapath and are you specifically saying that you'd want to prevent commercial activity on the fediverse at the protocol level?
That's something that's much more enforceable at the social layer, with server policies.