http://gameinfo.na.leagueoflegends.com/en/game-info/get-started/summoners-code/
4
Enjoy Yourself, but not at Anyone Else's Expense
"Short is the joy that guilty pleasure brings." -Euripides
Making games is our business, so it should come as no surprise that we want you to have a lot of fun. We want you to get excited, to have tension-filled moments, and to celebrate your success. This doesn't mean that we're okay with you ruining anybody else's day.
Remember, taking a jab at your friend in the middle of the game is a lot different than making a glib remark at a complete stranger. Someone who is unfamiliar with what you consider playful may take your comment as an attack and react unfavorably. If two players on a team start fighting, good communication and teamwork become nearly impossible. Once communication breaks down, the likelihood of victory is drastically diminished. It isn't uncommon for simple, good natured teasing to spiral out of control into a loss, so do yourself a favor and don't run the risk of sabotaging your own success.
6
Show Humility in Victory, and Grace in Defeat
"To be humble to superiors is duty, to equals is courtesy, to inferiors is nobility." -Benjamin Franklin
Having a great game is one of the biggest joys that League of Legends can bring you. But always bear in mind that when you're relishing that landslide victory there is someone on the receiving end that is probably ripping their hair out. While it's alright to celebrate, make sure that you keep any gloating (or any other mode of self-indulgence) out of all chat. Instead, thank your opponents for the game. After all, despite their best efforts, they just made you a very happy person.
Moreover, if you've just lost, avoid pointing any fingers or deploying excuses. Even if you had a great game, it's not alright to blame your team. You had five opponents in that game, and - seeing as you just lost - chances are that they had something to do with it. We all know that losing can be frustrating, particularly if it's a close game or one that's completely one sided, but nobody likes a sore loser. Instead, thank your opponents for the game, and take a moment at the end of game screen to ask what you could have done better. If you're polite, you might pick up a few pointers that can help you counter your opponent's strategy in the future.
TLDR: no
