The concept of 'Crown Immunity' is a complex legal matter, but you will find out SOMETHING at least about it if you click
http://www.guardian.co.uk/racism/Story/0,2763,1803
21,00.html
and read the material. The Crown - ie the Queen in effect - IS the law, in the sense that we have here in Britain a CROWN Prosecution Service to bring criminals to justice in CROWN courts etc. These prosecutions are made on behalf of the Queen, so it's difficult to imagine how she herself could be prosecuted. If you click www.bbc.co.uk/hi/english/uk/newsid_61000/61703.stm you'll find an account of the falling plaster incident.