[ejr]

I'm unclear as to what you mean by that last sentence. If someone is running a message system that is distributed and keys to encrypt and decrypt are store locally, not on the server, then why wouldn't it be secure? The message system may be anything as simple as an addressing system

Ex: Email, which is run by any number of providers, however if an email client is configured to use PGP and access is via POP/IMAP and not webmail, it's still secure as far as we know. A message system that may not be email, but still doesn't store keys on the server, still provides no way for cops to read it. Except perhaps to see some message was sent, not what the message was.