We are talking legal obligations.

If you remove content you posted somewhere in the fediverse, your server will send “delete” activities to other servers anyways. But your server does not know whether those other servers actually do delete it.

“Knowingly” is a big word given that Mastodon GmbH has been transparent about not having extensive legal knowledge in-house and being dependent on their probono lawyers. Which is completely understandable given their company & team size.

There is no legal precedent, but most likely you would only have to prove deletion on your own server.