As a team it is valuable to establish some common values or ways of working, and to write them down as a team charter. However, even when written down, it is not uncommon for them to become out of date and unused over time.
Often when teams form they are buoyed by the chance of success, the opportunity to do something great, to work with new people. In this frame of mind, they resolve to be discipline in practice and process, and at this point they choose to establish and write down these common values and principles.
These rules help the team self-regulate rather than relying on management or a scrum master. Over time the team members forget the qualities the once held dear. It is important to review and renew your teams vows every few months or when there is personnel changes.
It is often preferable to keep a rule, so if in doubt err on the side of caution – if you are concerned that removing a rule will make the situation worse, keep it
It is imperative to get consensus, otherwise the charter is liable to fail in its purpose. If you find that rules are implicitly followed and no longer a point of contention or confusion, then remove any physical/digital reminders or triggers – This is a sign of a maturing team. Do bear in mind if the team changes these implicit rules might not be so obvious to someone new.