But EU interoperability laws are cancelled out by DMCA (aka EUCD). That’s why reading a DVD with VLC has always been “technically” illegal.
If Apple is able to update the protocol in such a way that it requires some kind of signed attestation from the secure enclave (basically a DRM) they’ll get legal protection.
Also. Nobody uses iMessage in the EU. It’s all WhatsApp here. Blue bubbles are an American obsession.
The recently enacted DMA requires interoperability. Unless Apple wins its case against iMessage being classified as a gatekeeper service, it'll be required to support interoperability. I'd be surprised if tricks like hardware attestation were compliant, unless Apple allowed other companies' hardware.
Furthermore some implementations cannot provide hardware attestation, so it probably couldn't be limited to implementations which can, if the EU really means "interoperable"
What exactly is considered bypassing DRM in the case of Beeper Mini, and what copyrighted content is the DRM protecting?
This might be news, but the DMCA laws don't allow you to restrict software which is compatible with your own, especially if the competitor never used your code.