You could also have the law enforcement public key that was compelled to be installed in your corespondent keyring, invisibly, re-encrypting all those messages for FB, LEA and IC. That way its all "end-to-end encrypted" and giant public messaging system can be selectively tapped by authorities. Everyone loses!
as of a few months ago[1] it seems like Facebook and other tech companies haven't complied with it yet. I think governments are still just pestering them about it.