All teams need ground rules. Ground rules, the agreed behaviors of the team, should be short, sharp, unambiguous, and unanimous. The best ground rules follow the goldilocks-principle – the exist but are not unrealistic.
Ground rules are worthless unless implemented. A light set of ground rules which have been fully implemented is always better than a heavy set of ground rules not implemented or observed.
This means that any violations must be dealt with early on, or else the ground rules are not worth the paper they are written on.