Can anyone comment on how this is likely to affect multinational entities like Apple? Given the Australian market is so small, would it not more sense to leave the jurisdiction entirely rather than compromise security? Same goes for App makers like Signal. Why bother with Australia? (I'm Australian, and really don't want to see this happen FWIW, but it seems the rational decision)
Closed tools like Signal, Snapchat, Slack, Whatsapp, iMessage, Messenger, Hangouts etc will all make the promises about privacy you want to hear, but at the end of the day they are closed source and updates or commands can be sent to your handset to send plaintext to their servers at any time.
The question is under what criteria this will happen. Insider abuse? Government order? To make money?
Trying to make it illegal for companies to do this sort of thing on a country by country basis is worth pursuing, but it is not a real solution. We need to stop trying to use the law to enforce security.
The solution is to use tools that take court ordered backdoors off the table. Support open and federated communications networks where anyone can build their own clients or servers where pressuring of any entity can't put community built clients at risk.
There are a range of clients/protocols that meet this criteria such IRC with OTR, XMPP, IRCv3, Silence, Matrix.org.
Take your pick, and convince your contacts to use that instead of companies where you have to just take their word for it they won't backdoor you as it suits them.