What about chain of command?

After condemning Notre Dame's Obama invite and then warning about protests against it, Bishop D'Arcy now says he may join in a protest. While this is good news, why can't he simply stop the entire event? As "king" of his diocese, shouldn't he be able to say the word & put an end to it? Is he implying that a school enjoys higher authority than a bishop - even though a bishop "reigns supreme" in the diocese (under the Pope, of course)? [4/17]