Which is correct: "grammar rules" or "grammatical rules"?

Which is one is correct English: "grammar rules" or "grammatical rules" ?

In my opinion, "grammatical" means "conforming with the rules of grammar".

Thus, "grammatical rules" should literally mean "rules which conform to the rules of grammar". That is surely not the definition of "grammar rules".

Yes, I think you are correct! Grammar rules means rules about grammar. Grammatical rules are rules that are well-written and grammatical.

I think this means you can have grammatical grammar rules. In fact, grammar rules should always be grammatical!