Hi Dathon Ohm,

I did a cursory review of your BIP proposal, not on the technical matter as there is no reference implementation available, but I did one on the legalities raised in the text (grep'ing the word "legal" one can find 15 references versus only 2 references to the word "technical").

Under European law, there is a clearly established line of jurisprudences exonerating internet service providers or hosting operators to have to install a system for filtering all electronic communications passing via its services which would apply indiscriminately to all its users for any kind of content (CJUE, 24-11-2011, aff C-70/10 Scarlet Extended SA c/ SABAM, CJUE, 16-02-2012, aff C-260/10 SABAM c/ Netlog). Rather to engage in generic filtering on the burden of services providers, courts have generally yielded decisions asking for fine-grained deletion of a specific content, as a safeguard of other interest at stake, notably users's right to privacy [0].

Further, in the eventuality of an extended filtering system would have to be put in place by a service provider, and if said filtering system design would be unable to dissociate between legal content and illegal content, the introduction of this filtering system would consistute an infringement of the freedom of expression and information (CJUE, 26-04-2022, aff C‑401/19). Those judicial decisions are litteraly encompassing peer-to-peer softwares in their scope, as somehow before Bitcoin, they was something called Bittorent.

Moreover, this line of jurisprudence underlights that any interference with one's fundamental right of expression should be lay down under clear and precise rules governing the scope of the interference. This is not a mere formality, as again and again too restrictives measures are strike down (CEDH, 02-02-2016, Index.hu/Hungary, aff. n° 22947/13). As far as I know, I'm not aware of any European continental country that has made a legislation on how one is allowed to use his right to the freedom of expression in the context of publishing stuff in a Bitcoin block.

Under the US law, I won't risk making legal comment for now, as for anyone who is following the work of the Electronic Frontier Foundation from times to times, there is a pending case in front of the US Supreme Court, Cox Communications, Inc vs. Sony Music Entertainment specifially on the liability of Internet service providers. But given that US culturally are more protective of the freedom of expression, this would be an even higher bar to restrain freedom of expression.

I concur with Gregory Maxwell. There is zero need to change the consensus rules.

In the idea one would like to limit one's responsbility arising from how bitcoin consensus data can be encoded or decoded to "obviously" "illegal" content (as strictly defined by a specific national legislation) [1], fuzzy encoders and decoders for end-to-end or point-to-point communication could be formalized as BIP documents, that would put an asymmetric cost on the decoders, with the upper bound being the impossibility of decoding.

Fuzzy algorithms is not sci-fi tech it's actually what is used for Minisketch.

Best, Antoine

[0] "Those addresses are protected personal data because they allow those users to be precisely identified" [1] This is not a mere technicality, under information theory, one could come up with a alphanumeric encoding algorithm that could certainly yield text-based religious blaspheme in a lot of countries in the world from years-old un-reorgable historical blockchain data. We're all used to "The Times 03 Jan..." in the genesis block, but it's just picking hex as a decoding algorithm...