Playing While High or Drunk Shouldn't Be Bannable
If someone is drunk or high in your games, let the player be. Report the player silently if you consider it a problem. If it really bothers you then go ahead and let the player know that it bothered you. However, chances are that the game will be more enjoyable all around compared to most games. I regularly get more honors while high than I do while sober. Ive played league while high, I've played it while drunk, I've done both at once. Let me tell some of you, who do not have the experience, what it is like to play league while Inebriated.
High: Ranked is fine. Your mechanics improve. Your decisions come quickly. You're relaxed and in control of your actions. Everything is hilarious, you're practically impervious to tilt. I've noticed no matter how much I smoke, this applies.
Drunk: Depends how drunk but don't play ranked. If you're buzzed, then you might make it through norms or arams ok. If you're drunk enough to fall out of your chair, then playing LOL is nearly impossible. You can't click anything accurately. Sometimes you might lose track of your character.
Both: Just don't do it, it's not even that fun.
Tldr: League is easier while high, and harder while drunk. Don't rage at your teammates for doing drugs. If you consider it a problem report them. Just do your best to have fun with your team, and it'll likely be any enjoyable experience for everyone.