Such restrictions are an infringement of civil rights. The firearms in question are not machine guns but are regulated as such. Said arms provide a more compact means of effective self defense than both their longer barreled counter parts (Which are longer and more difficult to use in confined spaces) and more effective than handguns (which are more difficult to use under stress).
Special permission from the BATFE to not only own but transport from one state to the other are required to own these firearms in the U.S. along with a $200.00 tax stamp and long arbitrary wait times.