Well i found it, and i understand why my friend diddnt remember why he got banned
Dear Summoner,
Internal audits by staff members of Riot have revealed consistent abuse of the “Report A Player” feature by your account within League of Legends.
Falsely reporting players over a large span of time dilutes the significance of your reports and causes unnecessary distress to the players being reported. Reporting players is a tool used to help improve the community rather than a tool used to threaten or bully other players.
Due to this toxic behavior, your account has been temporarily suspended.
Please note that this is a temporary suspension to serve as an official warning. Moving forward, be mindful of who you are reporting as falsely reporting players is not only against the Summoner’s Code, but also negatively effects the League of Legends community. Failure to adjust your in-game behavior can result in additional punishments.
League of Legends Summoner’s Code: http://euw.leagueoflegends.com/articles/The_Summoners_Code
LOLOLOL
you can lock it tho