Can we change the bans?

So I was in champ select, and this guy declared he wanted to play Yasuo, and said "I only mid", and I said no to him, and because of that, he banned Taliyah, then someone on our team banned his Yas (Which was not cool), he chose Taric and went mid anyways then... it's happened to me multiple times... Can we please make it that you can't ban champs that are declared?