Comment by piltdownman

WhatsApp already does it for unencrypted messages for about half of the EU under the purview of the rules of lawful interception obligations for NI-ICS, as well as Norway, Switzerland and the UK.

When they want to read encrypted messages they seize the phone and use Cellebrite or similar 3rd Party tooling to gain physical user-level access. No need for cert-pinning or esoteric MITM attacks.

N.B. China does not allow WeChat to have e2e encryption.