Exception to the "... and me / I" Grammar Rule?

Look at the sentence: "...BY John and me." Me is objective case after the preposition 'by.' If you said "John and I are going to the movies," then I is correct because it is nominative case as subject of the sentence. So you need to see how "I" or "me" is being used; same with 'him, he,' and 'her, she.'