Jupp
Explorer
I think most rules are self-established. At least that is the case in those groups I play in. None of the DMs I know of actually has those rules written somewhere, they just came into action over time and people (more or less) stick them since then. And since there are always exceptions to the rules and roleplayers are of chaotic alignment by nature it doesnt matter a bit if those were written rules or not
You try to follow the rules but no one gets angry if there's the occasional slip. It's a game after all and there are already enough rules in the books.
