Ellroy's Chandler and Wambaugh Rule

Ellroy's Chandler and Wambaugh Rule is just something I thought of and then discarded, never to be referred to again. Even if I wanted to write something about it, I've long since forgotten what it means. Nevertheless, it seems I have mentioned it one time throughout. Maybe you can figure out what it's about by reading one of the following...

There are one film covered by Ellroy's Chandler and Wambaugh Rule