Having to justify WHAT we own is the reason this can't work in the US. It's the Bill of Rights, not the Bill of Needs. None of anyone's business as long as my firearms are legal and purchased legally.
The damned gun control people will probably try to use this idea to control our SECOND ADMENDMENT RIGHT so that they can (in the long run) have their own little security force. Hopefully the folks in Australia will be able to get their gun rights restored.