Rules?

I used to go to a private Christian school when I was younger (had good relationships with a couple well known colleges), and my pastor told me that demons and angels had a certain set of "rules" to follow.

I was wondering if anyone can elaborate on what these rules are and also how they came to be. The only one I remember him saying was that a demon or angel could not directly interact with us.

I know it' a dumb question, but any insight would be great.