The Trials of Cat People, Even Powerful Ones

It seems His Holiness Benedict XVI has been sneaking out at night to visit his old apartment. Dom Bettinelli suggests he's visiting his cats, who cannot live with him in the papal apartments, since pets are banned from the Vatican.

But couldn't he just, y'know, change the rules, or grant himself an exemption? He's the Vicar of Christ, for goodness sake! The leader of the Church Militant! He's Pope! Who's going to stop him? Was the "no pets allowed" rule infallibly defined by one of his predecessors on the Throne of Peter?