What I wonder about child abuse in the Catholic church

What I wonder is, with all the evidence now available about Bishops and higher ecclesiastics moving child-abusing priests around from job to job, why is this a matter for civil action by the victims and not criminal investigation by the police and FBI? Isn't there probable cause to believe that church officials knew about serious crimes and not only didn't go to the cops but actually facilitated the continuation of the crimes? Why hasn't the FBI subpoenaed church personnel records? In this respect, how is the Catholic church not a criminal enterprise?