People have to sign things in order to participate. From elementary school to the NCAA, one can’t participate unless they agree to do or not do certain things. This we (mostly) easily accept, and regardless, the rules are really clear.
You likely have written rules for your team, no matter what type of team it is. Perhaps a handbook, employee guide, posters in the lockerroom or a contract to sign.
On the flip side, many of us have more unwritten rules than written ones. “Work hard”, “show respect”, “be a good teammate”, are all big picture unwritten rules.
Does everyone on your team know exactly what is meant by those unwritten rules? Do you know?
Perhaps you also have some that are similar to these: “freshman do the grunt work”, or “the head coach is always right”.
It’s time well spent to investigate and know what the unwritten rules are on your team–you may not even know that they exist–and to clarify the ones you like. Even more importantly, shine light on the ones that are not valid or helpful to your team (“we drink a lot on Saturday nights”), and rid your team of these unhelpful rules.