system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How WhatsApp can allow reporting of messages and still be considered as e2e encrypted? Can the app itself automatically "report" all the messages if requested by the police without user action?
gpt
It's pretty simple....when you view a message on your device it is decrypted on that device. When you report a message, your device creates a new encrypted message between you and Facebook that contains the contents of that message (and the 4 previous from what I've heard) and (likely) the user you received it from.  

So from there, because you made a new message the original is still e2e encrypted, *and* the new message (the report) is also e2e encrypted.  

It's no different than showing your screen to a friend. They were not the intended recipient but now they saw an e2e encrypted message without breaking the entire e2e encryption process.  

EDIT: As for the 'automatically report', theoretically yes, it could, and your primary protection against that is hoping you trust FB enough to not build that in. Though if they did do that and word got out, people would likely move away from the app which would be bad for FB.