Not even the current POTUS seems to understand the constitutional make-up of the government: The Legislative Branch (Congress & Senate), The Judiciary (various federal courts and Supreme Court) and the Executive Branch - the POTUS and Secretaries themselves.

One of the tools of the Judiciary is the various law enforcement agencies - FBI etc.

The idea is that the law enforcement agencies report to and advise the Judiciary.

Not the other way around, as The Donald is finally finding out.