What I think surprisingly many people don't seem to understand though, is that there are no exact rules when it comes to languages (if there were, languages would never evolve). A native speaker will really only be able to use his "native authority" when it comes to the specific regional and sociolectal way of speaking that he grew up with.
I remember a test where you were supposed to put prepositions into empty gaps in various sentences. The test would then try to estimate what part of the English speaking world you were from (or if you were a non-native). I cannot attest for how accurate…