shooterdownunder, it seems to me that there is a misunderstanding about the difference between an outright ban and a de-facto ban. While it is theoretically possible for someone to legally posses a "category D" firearm in Australia, thus they aren't outright banned, the regulations and costs involved with doing so are so heavy as to prevent the vast majority of people from owning such weapons thus creating a de-facto ban.
A parallel here in the U.S. would be post-1986 macnineguns. You see, machineguns as well as some other types of weapons like suppressors and short-barrel rifles and shotguns are regulated and registered under the National Firearms Act of 1934. In 1986, an amendment known as the Hughes Amendment was added to the Firearm Owners Protection Act which closed the NFA registry to machineguns except to military, law enforcement, and those possessing a Class III dealer's license. This means that unless one falls into one of the three aforementioned categories, you cannot legally posses a machinegun that was not registered under the NFA prior to 1986. Because the vast majority of people are not military, LE, or in possession of a Class III Dealer's license, they cannot legally own a post-1986 manufactured machinegun so the result, for the vast majority of people, is the same as an outright ban.
A parallel here in the U.S. would be post-1986 macnineguns. You see, machineguns as well as some other types of weapons like suppressors and short-barrel rifles and shotguns are regulated and registered under the National Firearms Act of 1934. In 1986, an amendment known as the Hughes Amendment was added to the Firearm Owners Protection Act which closed the NFA registry to machineguns except to military, law enforcement, and those possessing a Class III dealer's license. This means that unless one falls into one of the three aforementioned categories, you cannot legally posses a machinegun that was not registered under the NFA prior to 1986. Because the vast majority of people are not military, LE, or in possession of a Class III Dealer's license, they cannot legally own a post-1986 manufactured machinegun so the result, for the vast majority of people, is the same as an outright ban.