> The laws of Australia prevail in Australia, I can assure you of that. The laws of mathematics are very commendable, but the only law that applies in Australia is the law of Australia.
This particular statement was widely lampooned in tech circles at the time as obvious nonsense. Yet it’s actually perfectly sound: legislation is all about restricting you from doing things that are possible. (Now some of the other stuff Mr. Turnbull said at that time was drivel; he seemed to be under the impression that it was possible to allow law enforcement to access end-to-end encrypted content without it comprising a backdoor, which the industry as a whole considers axiomatically false.)
It’s the government’s prerogative to ban mathematics. And indeed they already have in various areas due to copyright and possibly patent laws (c.f. illegal numbers). Now I personally think they would be unwise to ban any form of encryption, but realise that they’re quite at liberty to not just try to ban it.