Some players grief teammates by banning their highlighted champ

How do you prove that this is the case without prohibiting legitimate cases where I go into a queue wanting already to ban Zed?

How do you effectively balance that player’s “right” to play a champion, and my right to ban the champion I want to ban?

For me, i have a set of 3 champs i look to ban, Leo, then Trynd, then Yi, in that order, i one is on my team i figure I will let them have a chance, even if they would not get it high in the pick phase.

It's annoying, but hard to prove. I've taken to only using pick intent AFTER the banning phase when I'm going to play something that my teammates aren't likely to be happy with.