The Tribunal was a system introduced in May 2011 by Riot Games Inc. to help discipline players and keep the community in check with the help of their peers. However, it has been disabled since early 2014, with replacement systems being slowly rolled out in the time since then.
What it Does
When a summoner logged into the Tribunal, they were assigned a case to review. Each case involved a summoner who was reported for any number of reasons on multiple occasions. The summoner reviewing the case was given chat logs, game statistics, and report details to help them decide if the offending summoner should be punished or pardoned. A summoner could also skip a case if they are unsure or uncomfortable choosing a verdict. The Tribunal did not judge afk / leaves however. These cases are handled by the "LeaverBuster".
All the cases judged or skipped, the end result, and how unanimous the decision was could be viewed in the Justice Review. Additionally, a could can be revisited to see the resulting punishment assigned to the offender (permaban, time ban, warning, pardon). The Justice Review also showed a summoner's: total number of cases reviewed, cases correctly judged (vote agreed with the majority), longest correct judgement streak, and ranking and justice rating. Summoners could also see how many toxic days they have prevented and how many players have been perma-banned from cases they voted on.
Summoners that voted on cases in the tribunal developed a justice rating which was calculated using their score and their right/wrong judging percentage. A summoner's score was increased when their vote agrees with the majority verdict. There were no rewards for obtaining a good justice rating.
Who can Participate
Any summoner that is level 20 (Formerly 30) who isn't currently banned could participate in reviewing Tribunal cases. A summoner could review up to 20 cases a day. Summoners received a Justice Rating based on how often their votes coincided with the majority vote on cases. On the contrary, if a player repeatedly voted against the majority, they would lose the access to the Tribunal. This system was used to encourage players to read thoroughly their assigned cases, instead of blindly punishing people.
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 received a certain number of "punish" votes (a number not divulged by Riot), they received a punishment intending to deter this behavior from happening again. Possible punishments included a warning, suspension, name change, or in severe cases, permanent banning. The Tribunal automatically assigned some low-level penalties to players, such as e-mail warnings. More severe cases, however, were reviewed and assigned punishments manually by Player Support. Punishment was not influenced in any way by the number of votes. Under special circumstances, Riot Games could even veto the verdict of the Tribunal.
On 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.
- 74% 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 could not issue permanent bans. When a player accumulates enough temporary suspensions (a minimum of five times, unless specially escalated by Player Behavior specialists ), the system flags accounts for manual review by Player Support teams, 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 information 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.
- At some point in the future, people may also be given rewards depending on their Justice Rating.