A league constitution is the written rulebook a fantasy league agrees to before the season: scoring and roster settings, the waiver system, trade and veto rules, the playoff format, payout structure, and the penalties for a missed lineup or an abandoned team. It’s the document a commissioner points to when a ruling is questioned.

The value of writing it down is that it converts arguments into lookups. When two managers disagree about whether a trade was legal or how a tie breaks, a constitution turns the dispute from a debate about fairness — which the commissioner can’t win, because they’re also a competitor — into a reference to a rule everyone accepted in advance.

Most platforms have nowhere to store this, so it ends up in a pinned chat message or a shared doc that drifts out of date. Keeping the constitution current and reconciled with the league’s actual settings is one of the quiet, recurring parts of running a league well.