Where do people get the idea that it is illegal to own a fully automatic firearm or an "assault rifle"?

It isn't illegal in some of the REAL states but in California they will not even allow you to have something along the lines of the S & W Governor or Tarsus Judge. These handguns will fire either a .45 or .410 shotgun shell. Some of the handguns they allow are only allowed in certain colors, perhaps nickel but not blue.