Should you be able to ban your teammates champs?
Why are you able to ban your teammates champions? There is nothing more tilting than your teammate banning the champ you are playing after you don't trade with them (or sometimes for no reason) and then putting a sly ":)" in chat. You can dodge, but not everyone enjoys the extra 5 minutes before a game.
Edit- comments are right, you should be able to ban whoever you want. But there should be something telling you that you shouldn't do it. For instance, in champ select, when you are choosing a champion that your teammate has already chosen it is greyed, but you can still click on it.