What it does
When a summoner logs into the Tribunal, they are assigned a case to review. This case includes another summoner who has been reported, for any number of reasons, on multiple occasions. The summoner reviewing the case is given chat logs, game statistics, and report details to help them decide if the offending summoner should be punished or pardoned. A summoner can also skip a case if they are unsure or uncomfortable choosing a verdict.
Who can participate
Any summoner that is level 20 (Formerly 30) who isn't currently banned can participate in reviewing Tribunal cases. A summoner can review up to 20 cases a day. As a reward for their participation, summoners whose votes coincide with the majority votes on cases will receive weekly bonus Influence Points for their time and they will gradually get more cases per day. Rewards are given weekly, after the judgment period on the cases ends. On the contrary, if a player repeatedly votes against the majority, he will lose the access to the Tribunal. This system is used to encourage players to read thoroughly their assigned cases, instead of blindly punishing people. The average award for tribunal per case is currently at 5 influence points.
The following actions are violations of the Summoner's Code and considered punishable offences:
- Explicit use of hate terms, racial slurs, cultural epithets, etc.
- Players who deliberately and viciously insult other players.
- Repeatedly negative, nonconstructive attitudes.
- Players whose teasing crosses the line, and who persist after being asked repeatedly to stop.
- Deliberately disruptive gameplay, such as intentional feeding or otherwise assisting the enemy team.
- Offensive summoner names.
- Honor trading.
It is important to note that occasionally having bad games is not considered a punishable offense, but it is possible to receive suspensions if deemed appropriate by a riot customer service representative as stated in the Tribunal FAQ.
When a summoner's case receives a certain number of "punish" votes, (a number not divulged by Riot) they receive a punishment intending to deter this behavior from happening again. Possible punishments include a warning, suspension, name change, or in severe cases, permanent banning. Every action taken against the player is automated, with very few exceptions depending on the severity of the case. Under special circumstances, Riot Games can even veto the verdict of the Tribunal, but appeals are not possible as customer service responds to requests for information with premade messages.
MetricsOn Friday, May 25, 2012, 3:55, Riot released the following Tribunal metrics:
*More than 47 million votes have been cast in the Tribunal.
- 51% of Tribunal cases result in a guilty verdict, with only 5.7% earning a permanent ban.
- 50% of players warned by the Tribunal just once never end up there again.
- Over 700 individual cases were personally reviewed by Lyte and Pendragon.
On December 21, 2011, Riot released the following Tribunal metrics:
- 1.4% of all players have been punished by the Tribunal.
- Over 50% of all punished players never re-offend.
- 94% of players who receive enough reports to face the tribunal are punished by their peers.
- Average player reports for the average one-time offender: 11
- Number of player reports accrued by the average repeat offender: 70
- Offenders lose games: 24% of offenders are on the winning team. 76% of offenders are on the losing team.
- Offenders make bad teammates: 71% of offenders are reported by their own team. 29% of offenders are reported by the enemy team.
- Over 16,000,000 total votes have been submitted.
- Over 80,000,000 influence points has been rewarded to voters.
- The Tribunal cannot issue permanent bans. When a player accumulates enough temporary suspensions, they are escalated to special Player Support team which reviews the player's behavior and determines if a permanent ban is warranted. 
- In the online Tribunal case review, a random sampling of games in which the subject player has been reported is displayed. 
- It takes hundreds of reports over dozens of games for a player to end up in the Tribunal. Not all games are displayed for Tribunal judges.  The average player has 20-40 reports per 2000 games. 
- Ratio of games to reports is included in the formula that determines if a player ends up in the Tribunal. 
- If a player is suspended by the Tribunal, cases that occurred before the suspension are no longer counted for purposes of sending the player to the Tribunal again. 
- Players who receive a warning from the Tribunal have their honor scores reset and their honor badges removed.  
- There is a method to discourage voters from spamming the Punish button. 
- Players who are repeatedly sent to the Tribunal, but are pardoned, have their accounts flagged for manual review. Rioters that review cases have access to more informational than Tribunal judges, such as pre and post game chat logs. 
- Players who have been punished will have their 'Ban level' go down over time if they do not incur further infractions. 
A number of features have been planned in the future to enhance the Tribunal system.
- Inclusion of pre and post game chat (such as the champion select and victory/defeat screens)
- Inclusion of whether players in the game were a part of a premade group or not.