Papal supremacy is what you are thinking of. The Pope can change interpretations where rules are unclear, but he can't say 'adultery is fine now kids, have fun'. He can't over rule God.
As have Catholic and Protestant churches. That's basically what theology is. My point was that these amount to the debates we see in the rules forums. Until God himself steps in and issues something definitive, such commentaries and interpretations are just personal opinion, no matter how well supported by RAW or RAI they may be.