> does Australia have constitutional or otherwise legally protected free speech
No. Australians have no direct freedoms at all. What rights they have are "implied" indirectly from other things such as that the federal government shall not restrict trade between the states (it's hard to trade if you can't talk ...). People talk from time to time about strengthening individual rights, but most Aussies couldn't care less and due to mandatory voting those that don't care will vote down just about any constitutional amendment making it extremely difficult for such reform to ever happen.