That's not entirely accurate. If you look at the jurisdiction of the NSW ICAC as an example,
... The ICAC deals with corrupt conduct involving or affecting most of the NSW public sector, including state government agencies, local government authorities, members of Parliament and the judiciary. Police and NSW Crime Commission corruption is dealt with by the Law Enforcement Conduct Commission.
Obviously the extent of the reach of an oversight body can be constrained by political obstruction at it inception. Which is perhaps why "Dracula shouldn't manage the blood bank".
