Also, ironically, making it encrypted would help him avoid jail. (I don't cheer on him being arrested, that's a horrible precedent).

Signal does not see groups, membership, content, ... They encrypt to protect the users, but also themselves. They can't analyze messages if they contain drug trades or child porn, because they are not in business of storing messages, they ship around encrypted blobs of data and they can't tell their meaning even if they wanted to. 

SimpleX goes even further - they don't operate infrastructure, anyone can run a relay. They are in a business of writing user interface for end to end encrypted chat protocols. Users use servers operated by third parties, that also don't see the content, in this case not even user identifiers (there are none on SimpleX). Each connection looks different, so you can't even write a proper court order, because it's very hard to identify what user it concerns.